* My hh ct 4 
he ga PRET toe 
Boarding 
eA seat 
; marae “ 
Pe ge a AS) Les ‘ yt 


4 


a 
ne ‘Ge i 4 ) rho nt F at D2 ae x Ue lif pray hs ' y i » 
Veo cite Wire sen eee) fr Foi fe 0 @ e ca 9 i Shae t hose paws rte : itt A Pe Ani ip ae ft Miah PS esta tiga es 5 ; 
108 Bit % ey en ey i PAL : Nyy " “hehe wien Phy ds: 
¥ (' i) fieneleaw fl pe 4 
hey Ue eA Fst Ni dy oie iba eae 
ii ‘ its? hie iy 
uff * duileatds 
Wk Se 


He RY et é 
ras wit es os Pte Ta at DO HER oh i ereeena taal itde a 
I an rar Nahe foe nes q sat g ti wie a) (3 Hi; : i F if Fr) iad Drea gr hee Me ests Pay fie oem i Fi ponte 


We 

Vk 

Sia Ny te, 3) 
ys es Seay: 


r 


1a ey b ¥ jor: 

1 QE Os oe IF Te bel Wry 5 ie hs 
Agate Me eit eg BRST Be i A nee Dope 
i$ S- Hie Oo AY Mc 9) ae 

YP Meteo gh Weise thy 
Ks Boe aaa ae) 


t 

5 hike Soka 

Rig hppa 
she 


shea g 
einstein 
i ah 

\ nk 


Ae Ref ie 
Tee Mt AL Ay 
fe P38 
we elas 4 Fe tee 
FAA Sea ie 0 Bs y fu ER ee 
WM SQ peat phe: BoM at ie ay HF ey 
eo ge fo Wiha te gig 4 
‘ 


f Be PO a at x j i Be opel Aa tay 
AAA Se A benehan as bale seal 4 . Hie) iy f i " i 
Ae -« ey tia | #3 i 4 E Wat an etic f Merlin fai 5 4 ): 
$6 eo uh ees eae he fae % *Y : Y Pe Nene ne Pu tars yf q 3 is KD aed BAS) fs ye PEA) Be doth | tee 
i av 2% +f ha é 4h BF uty ine A we Sih e ae iL Ai tee | ler a 
ae Ne atabiegunas ms EAN poe AN rn ee Og ih ; SS Paghe alsin yin i 


WF MU 
4 \ ie eal +o et eae 
abhi ee oe , a Kg pie (a ames es 
bs sis : h 3 oi? ane) tpi th 
oth 


# 


a Mh ig i 
Oy pedo hay Pa rey 
h Toy Baia eas fi 
¥ eA 


ie ip 

Robie M Dosh 

a eee th 5 o ha hes 

AeA! ne Seca hy) 3) vi i 

4 hae fed 

Reg aes 
hae 


ah ‘ % 
te (Weak ay tPok ipatge bak 
Diag Doth te Ap be vod eh 


Bid, 
Hah 
4 ae be 
, in Pata eas fy 
A a We dedi ? a ii a a 
‘ : ce ; ’ Sa ato 
eS SEN i yan Ae 
Che Wei Mir aah g 4 iad ey 
un ebro ae 3 * i 3 1 
f Hopaeito a i 
ayy ey 
A 
it eR ee 
i‘ 1 ya badh fb 
Ban's 
Heh, 


oy " ws E 

tae yan 

4 if my ih eles y ‘f ny oe 

aL ae ci 5 a by Ah Ta hy 

Deh ene bait ds Pht 4 me tae ay hy nie th 

Wn ele f a W5ei " HY a IRAE GE 
enka wake : Mtshasts ee ( y oly 
cee : eh ata 


HRY ACES een 
pork etme! Pay oy 


wih A hectic an : ! : ; ‘alas 
9, eth teak Wee wom th ht By ? ee Ke Dei “eRe eA is 
Ay tie 303 ep dete Viale ght ‘ ‘ "y 
De Hy BL obo Se 4 . 
iar 


aris 
Powe late «i oko 
yaeay f a y Fee ty bgeh 
& By Bercy eA. 4 \ f 
gH A Ah AG D0 
SW eorandiibs ot) Wie 


Se 
frat 


440 


Ze 


‘ 5 


Ys 
sivea hey 2S 


; fel EL N 
Kip HE TD eth 
Yor ie aah 


he WA Yh 
. 


a ie 
tx ait NVM 


: i 
a 1 iy f 
i Ans ir e 
A WEN Natick oy ae tient 
is tee Arte hahe c i 


Ys yt 
i aint 8 
sate ia ey my iy 


ani 
AGA te th 
a we 


bs 


co 4 
\ AHA i 
SENS 
uate Mus ON 
one Sih eins 


{ieee Beate Ri ; iy ee 
WN ODO 4 ei Ny e.% Oa Qe 





LIBRARY OF THE 
UNIVERSITY OF ILLINOIS 
AT URBANA-CHAMPAIGN 


abotewe tay 
CLS 
AT a 











® 7 - : 
o *f | 
7 _ 
A ee 
iM 
/ 








Digitized by the Internet Archive 
in 2022 with funding from 
University of Illinois Urbana-Champaign 


https://archive.org/details/californiaearthgs/11cali 


THE CALIFORNIA EARTHQUAKE OF APRIL 18, 1906 


REPORT 


OF THE 


STATE EARTHQUAKE INVESTIGATION COMMISSION 





o vt : 7 
vo 1) 
' 
ota, . 
A ABO 
STATE EARTHQUAKE INVESTIGATION COMMISSION : 
F ; : ~ 
ANDREW C. LAwson | A. O. LeruscHNER 
G. K. GiLBErT GrEoRGE DAviIpson 
H. BF. Rerp hae Wy CHARLES BURKHALTER 
J. C. BRANNER W. W. Camppenn 
és TRA Te 
* - ? 
’ 
| 
x 
a Bt a ; 
; sg 


THE CALIFORNIA EARTHQUAKE OF APRIL 18, 1906 





REPORT 


OF THE 


STATE EARTHQUAKE INVESTIGATION COMMISSION 


IN TWO VOLUMES AND ATLAS 


VotumE IJ, Parr II 





WASHINGTON, D. C. 
PUBLISHED BY THE CARNEGIE INSTITUTION OF WASHINGTON 


1908 







= ; yo 
. “yy 1 an 
TPES 2 PPG LET Ae 


CARNEGIE INSTITUTION OF WASHINGTON = 


Pusrication No. 87, Votume I, Part IL : a 


ive 


A 
Jt : 
t 
a * q ae 
cag, Notovaoy Bress 1 
J. 8. Cushing Co. — Berwick & Smith Co, | ; 


Norwood, Mass., U.S. A. 


; _ vi? 
‘7 i ‘ Lee'tar P use gare o16 ) Riga pe ee a 


- : 
> ‘tS 
: ) - ~ 
: a tt 
. a | u , J 
= . 
° ve a 7 
a | 


PART TWO. 


TSOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY — CONTINUED. 


AREA OF THE SANTA CRUZ QUADRANGLE OF THE JU. S. GEOLOGICAL SURVEY. 


The distribution of intensity in the area of the Santa Cruz Quadrangle was studied by 
students of Stanford University, under direction of Prof. J. C. Branner. The con- 
tributors to data embodied in this part of the report are Messrs. R. V. Anderson, H. W. 
Bell, B. Bryan, R. E. Collom, R. Crandall, P. Edwards, H. P. Gage, F. Lane, R. Moran, 
R. L. Motz, A. F. Rogers, 8. Taber, A. F. Taggart, F. W. Turner, and G. A. Waring. 

Stanford University (J. C. Branner). — Referring to the group of dwellings southeast 
of the University quadrangle, there were 61 residences on the campus of Stanford Uni- 
versity at the time of the earthquake. Out of 140 chimneys on these buildings, 104 
were thrown down, or 74 per cent. The plaster was generally badly broken on the first 
floors of these buildings, and less injured tho generally more or less cracked in the second- 
floor rooms. At No. 138 Alvarado Row, first floor, several pictures 18 inches across, and 
hanging by cords 4 feet long, were swung so far that they were left with their faces to 
the wall. On the corner of Salvatierra and Aguello Streets, a frame building occupied 
by the Chi Psi Fraternity was so badly wrecked that it had to be abandoned. The 
injury done this building was due to its having stood upon posts 4 feet high and not well 
braced; the swaying of the building threw it off these supports. 

President Jordan’s residence, west of the quadrangle, had 38 brick chimneys, all of 
which were thrown down; the plaster was so badly injured that the first floor, the ceilings, 
and part of the second floor had to be replastered. This building rested upon a brick 
foundation about 4 feet high. 

The Stanford residence, a mile north of the quadrangle, was so badly wrecked that it 
has since been torn down. ‘The original building was of brick, and wooden additions 
had been built on the northwest and southeast sides of the brick portion. The additions 
stood upon wooden uprights 4 feet in length. The southeastern wooden addition was 
thrown from its supports and fell away from the older brick portion. The brick portion 
of the structure was badly shattered. In the grounds and parks about the residence 
there were many marble and bronze statues from 4.5 to 5 feet high, standing on pedestals 
from 2 to 4 feet high. These were all thrown down, except a few that were very securely 
bolted to heavy pedestals. There was no uniformity in the directions in which they fell. 

Between the Stanford residence and the museum, a large 2-story brick winery had 
the 4 gable ends thrown down. ‘The northwest gable fell into the building, the south- 
east gable fell outward, while the gables on the northeast and southwest sides fell outward. 

Mr. Charles G. Lathrop’s residence is not on the valley floor, like the other buildings in 
the immediate vicinity of the University, but stands on a hill of sandstone nearly 300 
feet above the level of the bay. Out of the 4 brick chimneys on his house 2 were thrown 
down; 2 water-tanks 53 feet high (10-foot tanks on 43-foot supports) were not injured, 
but about two-thirds of the water was thrown from them. 

Professor Durand’s house, south of the quadrangle, is on a hill 160 feet above the bay 
and stands on the upturned edges of gravel beds that underlie the Santa Clara Valley. 
Of 3 chimneys, 2 were thrown down, and the plaster was cracked on the ground floor. 

Of the University buildings proper, some were unhurt while others were completely 
wrecked. (See plate 1028.) They all stand upon the loose gravelly loam of the Santa 


364407 ae 


256 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


Clara Valley floor. As a rule, the older the buildings were the better they withstood the 
shock. Much damage was done by the throwing down of stone chimneys. The 150-foot 
stone chimney of the power plant was thrown down, crushing part of the boiler house 
and killing a fireman. The double-flued 60-foot chimney of the assay laboratory fell. 
The large stone chimneys of the dormitories were broken off at the roof edges and fell 
into the buildings. At Encina Hall, the men’s dormitory, one chimney fell thru the roof 
and carried down a tier of rooms into the basement, killing one student. The south ends 
of the wings of Encina Hall were so badly cracked that they had to be entirely rebuilt. 
It was found that the injury done to the ends of the wings was due to the relation of 
these particular walls to the roof beams. Excepting the cracking of plaster, Encina Hall 
was not otherwise injured, tho it is a 4-story building, with basement and attic. 

The chimneys also fell from Roble Hall, the women’s dormitory, and did some damage 
to the roof and upper floors; but the building, which is of concrete, was otherwise unhurt. 

The Chemistry building had 82 tile-lined stone ventilating chimneys projecting 12 to 
16 feet above the roof, besides 2 ordinary stone chimneys; these were all thrown down. 

The stone tower of the church was shaken to pieces, and in falling destroyed the parts 
of the roof immediately around the tower. The north gable end of the church was 
thrown outward into the quadrangle. (Plate 103B.) 

The top of the memorial arch was broken off down to the upper part of the frieze, and 
in falling it wrecked adjacent portions of the arcades to the east and west. (Plate 103a.) 
The parts of the arch left standing were cracked. The 2 smaller arches at the east and 
west ends of the inner quadrangle were slightly cracked near the top, but they were not 
seriously damaged. 

Besides the damages to the church and the memorial arch, the most serious injury to 
the quadrangle group of buildings was done to the larger structures. The 1-story 
buildings, especially those that had been standing for several years, were not damaged 
beyond the occasional cracking of plaster; and even in these cases the injury was found 
to be directly related to the method of supporting the roofs upon the walls. The statues 
of the front fagade were dislodged and one was thrown down. (Plate 1008.) 

The I-story buildings in the outer quadrangle had all been lately put up, and these 
were somewhat cracked, tho none of them was seriously hurt. ‘The cracks were generally 
about the ends of the buildings and along the tops of the walls where the roof timbers 
rested upon them. ‘The higher buildings of the outer quadrangle were more seriously 
damaged, especially those situated on the corners. These buildings are all three stories 
and basement. ‘The towers on the inside corners of these buildings were all more or 
less broken and require rebuilding. The Civil Engineering building — three stories and 
basement — at the southeast corner of the outer quadrangle had its outer walls badly 
cracked, especially on the north face, and about the tower at its northwest corner. 
Inside the plaster was injured more or less all thru the building. 

The Geology building, at the southwest corner of the outer quadrangle, was the last 
building of this group to be put up. It was a 3-story structure, and had barely been 
finished; but it was not yet occupied when the earthquake occurred. Sections of the 
walls were thrown down from every face of the building. These sections extended 
from the eaves down to the second floor. The tower at the northeast corner was badly 
cracked and part of it fell. The plaster was broken on all the vertical walls, both on the 
outside walls and on the partitions, showing that there was much internal wrenching 
of the building. The walls of this building will all have to come down and be rebuilt 
from the foundation. (Plate 102a.) 

The inner arcades of the quadrangle were not much affected. At one place on the 
south side of the memorial court, where the arcades are not directly connected with any 
other building, they were so violently swayed that they seem to have come near falling. 
They were found to be 7.75 inches out of alinement after the earthquake, and the tops 
and bases of the supporting stone columns were chipped off. (Plate 105s.) 


PLATE 99 





A. Wreck of 2-story brick building, San Mateo. Per J. 0, B, 





B. Wreck of 2-story brick building, San Mateo. Per J.C. B. 


7a 


sy 


4 f 


ae 4 
a 


SANE sh 


ay 
és 


bm dm 


Ss 





100 


BEAA E 





A. Trestle carrying a 30-inch water pipe across Frawley Gulch demolished by shock. R. L. H. 


B. Statue of Agassiz thrown from its niche above arches, Stanford University, Per J. 0. B. 


2 wy 


ra 


“ 
— 
y 
¥ 
4 
os 


Be ortega mom? 





Rory OF WE 
¥ arty Ws Wh 
. 
. 
F t 
‘ 
a, 
‘ fi 
ey, ay 
ka yew 
‘ 
(~~ 
re U 
oC eee 
- 9 a 
7 ‘¢€ 
a a = 





A. Destruction of arcade at Sacred Heart Convent, Menlo Park. R, C, 





B, Gateway of Campus, Stanford University. Per J.C. B, 





es ase = ehh ee ore eet 


»*% 


‘ 
. 
x aw Sh a = 
ai 
7 
' 
i, 
‘ ‘ ‘ a 2 
’ 
i ; 
‘ 
‘ > Pils 
' Pid rats 


eo es Te poner Sn pes eyes Ping! 
alt UT Lae eee 
, ‘ A f a tae © ay 
© 


i. wy 





sas * 
- 7 Th os 
ty 
- yy = 
on Pt 
sé 
. * 
; 
. 
yh 
7 1, 
’ Ca 
«) ‘ 
“4. 
« 
‘ 
‘ 


eda ey Keele et or eee mages = + 


‘ 
« 
3 
‘ 
« 
. 
‘| 
3 
\* 
1 
* 
‘ 
~ 
‘ 
. 
.7 i 
MV 
= ee Ske et 
j 
é 
, 6 ¥ 


e¢ 
aN 





102 


PLATE 

















A. Geology Building, Stanford University. Per J.C. B. 
B. Panorama of destruction, Stanford University. Memorial chapel in middle right. Per J, C. B. 


, ee 





ee 
“7. 
MS 
> 
*, 
aes 
. 
Hr ; 
¥ OF ILLiNul 
. 
; 
« 
: = 7 - 
; > ne een @ . 7 
. BEIT T = Oe 
7 Sh Loe 
t 
¥ — a 
. a 
f 7 ‘\ 
Sn eat oy ee Oe 
‘ * 
. F 
oil 
"i - ' . - v 
‘a \ 7 @ Pa’ "Oa 
. > oe | a 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 257 


The arcade along the south side of the outer quadrangle that was not directly connected 
with the other buildings was completely wrecked. The arcade in front of the French 
building on the east side and a corresponding piece in front of the Physics building on 
the west side of the outer quadrangle were thrown down. South of the business office, 
parts of the outer arcades fell. This is on the east side of the quadrangle. Parts also fell 
south of the Mineralogy building, on the west side of the outer quadrangle. (Plate 105.) 
The arcades around the memorial court are only partly in direct connection with buildings. 
The free portions appear to have swayed so far out of the vertical that the bottoms of 
the stone columns supporting the arches were chipped off, or cracked at their bases. 
The 2-story woodworking shop of brick, south of the quadrangle, was badly damaged; 
and the forge building, next to it, also of brick and 1-story, was cracked. 

The chemical laboratory, a new stone-faced building (two stories, attic and basement), 
was so badly cracked that most of the walls have to be rebuilt from the foundation. 

The new gymnasium, a stone-faced brick building, was totally wrecked. (Plate 
1048.) It had just been put up, and the inside work was not yet finished. The new 
library, also a stone-faced brick structure, was completely wrecked except a tower of 
steel on which its central dome still stands. (Plate 1044.) This building had just been 
put up, and was not yet finished on the inside when the earthquake occurred. The 
Museum building consisted of an older central portion built of concrete, and extensive 
additions of brick had just been completed. The new brick portions of the building were 
almost all thrown down, but the older concrete part was unhurt. 

The ornamental stone gateway at the entrance to the university grounds, near Palo 
Alto, was thrown down. (Plate 101z.) 

The water-tank at the Faculty Club-house was wrecked and a water-tank in the fields 
east of Alvarado Row was overthrown. ‘The large covered tanks west of the stock farm, 
beside the county road, were not thrown down, but much water was spilt from them. 

Palo Alto (A. F. Rogers). — The most interesting effects of the earthquake in Palo 
Alto were those which showed movement of buildings and those which gave evidence of 
twisting. A number of buildings moved toward the southeast 1 to 6 inches or more. 
Some buildings were left out of plumb and usually they were inclined to the southeast. 
In other cases, buildings collapsed and fell toward the southeast. It should be remarked 
that practically all houses moving to the southeast were those situated on the streets 
running northwest-southeast. Very few buildings on the avenues (running northeast- 
southwest) were moved at all. The moved buildings stand approximately at right angles 
to the fault-line southwest of Stanford University. 

A change in the direction of the earthquake movement is suggested by the fact that in 
several cases the chimneys were apparently twisted from their normal positions. The 
same is true of several houses that collapsed. The twisting was clockwise in some 
cases and counter-clockwise in others. A remarkable case of twisting was shown in the 
house at 727 Cowper Street, where picture frames were tilted from the normal positions. 

Chimneys were mostly knocked down, those that remained standing being for the most 
part in the centers of the houses. The direction of their fall was apparently accidental. 
A curious case is that of three 1-story frame houses, exactly alike, at 317, 323, and 
329 High Street. The chimney on the house at 329 remained standing, while the 
chimneys on the other two houses fell. 

The data upon which these conclusions are based follow: 


737 Channing: Small one-story frame house without foundation; chimney standing. 

845 Webster: One-story frame house with wood foundation; chimney standing. Chimneys were 
thrown from the two one-story fraine houses next to it. 

434 Middlefield: Two one-story shingle houses; chimneys standing. 

427 Middlefield: One-story house; chimney in the center of the house stood. Next door, same kind of 
house, chimney at end of house fell. 

667 Hamilton: One and one-half story frame house; chimney in center of house stood, while one at 
side of house fell. 

557 Hamilton: Two-story frame house; chimney standing. 

8 


258 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


Hamilton and Middlefield: Two and one-half story frame house; chimneys standing. Chimneys down 
in houses around it, both one-story and two-story houses. 

368 Lytton: Very small frame house without foundation; chimney standing. _ } 

Hawthorne near Waverly: Several small houses; chimneys in center of houses standing. Side chimneys 
on small houses across the street from these were down. 

171 Cowper: Tiny one-story frame house; chimney on side of house standing. _ 4 : 

317, 323, and 329 High Street: Three one-story frame houses exactly alike, and chimneys in same posi- 
tions on houses. Chimney at 329 standing; the other two down. ; 

310 High: One and one-half story house; chimney in center standing, one on side down. 

Kingsley and Bryant: Two-story stucco house; chimney standing. No damage. 

1329 Waverly: Low one-story shingle house; rather high chimney standing. 

Boyce Avenue: Two-story rather low frame house; chimney standing. ; 1 

Guinda Street: Two frame houses, one one-story, other two-story; chimneys standing. Chimneys fell 
from houses on both sides. , 

Hamilton and Fulton: One and one-half story frame house, chimney cracked but standing. Very 
small house next to it, chimney down. 

465 Hawthorne: One and one-half story house (first story brick); apparently no damage except chimney 
down. 

347 Melville: Two-story stucco house; chimneys all down. 

Forest Court: One very low frame house; chimney down. 

253-255 Homer: Two-story double stucco house; plaster slightly cracked, chimneys down. 


EVIDENCES OF TWISTING. 


1110 Bryant: Small one-story frame house; chimney at center of house twisted slightly counter-clock- 
wise. 
121 Emerson: Small one-story frame house; chimney in center twisted clockwise. 
Waverly near Lytton: The Palo Alto Academy, an old two-story frame house, completely collapsed, 
falling toward the southeast and apparently twisted counter-clockwise. 
Emerson, near University Ave.: Two-story frame house was moved off its foundation toward the south- 
east, and twisted clockwise. 
711 Cowper: Pictures on walls; some remained straight, others 
p------- 5 were twisted as shown in the sketch, showing the four 
\ fie SCs wares : walls of the room. The pictures on the northeast 
A f and southwest walls were observed in one room and 
4 those on the northwest wall in another room. (See 
fig. 55.) 
t 
{ 


MoveMENT OF BUILDINGS. 


627 Waverly: Two-story frame house high above the ground 
and resting on brick foundation; lower part of house 
moved toward the southeast so that it had to be 

! propt up. 

tae----- -~--------/ 711 Cowper: One and one-half story frame house high off the 


| ground; 6 inches out of plumb in rear. 
745 Cowper: One and one-half story frame house, high off the 
1 


ee 


ae aay 


ground; several inches out of plumb. 

538 Emerson: T'wo-story frame house; first story moved 2 
inches toward southeast. 

(SESS ay 439 Alma: One-story stable moved a little to the southeast. 
Fic. 55, — Diagram showing displacement of 129 Emerson: Two-story frame house several feet above the 
pictures on walls of rooms. ground was moved 3 feet toward the southeast and 
set down on the ground. 

Luscher Building, 251 High: Two-story frame building; moved toward the southeast several inches, 
and apparently twisted counter-clockwise. 

Palo Alto Hotel, Alma and Lytton: Three-story frame hotel moved toward the southeast. 

Greenhouse, near San Francisquito Creek: Very little damage; afew panes of glass broken. The benches 
moved toward the southeast from 0.5 to 1 inch. 

Ruthven and Cowper: New one and one-half story shingle house with concrete foundation; chimneys 
standing. House propt up on southeast side. 

Dudfield Lumber Yard: Piles of lumber moved in various directions, but mostly toward the southeast. 

Forest and High: Lumber shed; lumber piles on each side of open central space partially collapsed. 
Lumber piles on northwest side moved toward the southeast; those on southeast side re- 
mained in place. q 

Bleiber Blacksmith Shop: Two-story frame building; lower story moved 4 inches toward the southeast. 

Alma, west of University: New three-story artificial stone building fell toward the southeast. 

Alma, east Beecher I) Avenue: New two-story artificial stone building; collapsed and fell toward the 
southeast. 

444 High: Two-story brick business house; first story moved toward the southeast. 


MISCELLANEOUS. 


The pases Ce San Francisquito Creek, at Bryant Street and Middlefield Road, apparently were not 
damaged. 

University Avenue and Romona Street: Jordan Building; three-story stucco business building. Plaster 
on first story badly cracked. 


a 


PLATE 103 


a eas 


=e 
ev 


ed 
al 
¥ 





A, Ruin of Memorial Arch, Stanford University. Per J. 0, B. 








B, Front View of Memorial Church, Stanford University, 





ee 
A we 


oe | 
a 1% 


PLATE 104 





A. Wreck of Library Building, Stanford University, Per J. 0. B, 





B. Wreck of Gymnasium Building, Stanford University. Per J.C, B, 


ay . 
ae st Be 


A 


ee a! 
te hott dah 
ih ow (perce 
, an: 





105 


PLATE 





Per J. 0. B, 


sity. 


Stanford Univer 


mg; 


Wrecked arches, Geology Buildi 


A 








B. Arches that moved on their supporting columns, Stanford University. Per J. C. B. 















- > 04) ee . wis heh Sb et ae PY to ” G > 
rp Py i rs he mi Ll or “ 
¥ 5 ioe Ne as Ey cath a - 
* ay . mrs , i 4 
j ¢ ? f/ i 
1%, a ee ee 
i * a Foo ; 
’ ae 
4 
¥ é ay 
. 
* tn 
an e 
ts 
i . 
: sit w 
© 
: cP ae 
a baad 
‘ i oe 
: . 
: . « ye ie 
val - $ é J 
. 4 ras” ree 
* ary pt} 
= > Ke 
“ ae. te 
- ba 
+ rn 
: > -; . be 
j ‘ 
- 
. ¥ 
; A 
® 
: : 
+ 
, “ 
. q 7 
aye’ ‘% ‘4 
‘ A - » 
‘ aie. 
‘ ~ ( ” 
~ ‘ 2 iy 7, 
é ray ‘ Nes 
if oe * : \ ie 
ait ' 
4 ey i ° ' 
: rs 
a ' bce iny 
ee , ’ 
3 A 
+ @ oo 
+ Ci i 5 
eran ‘ Ye 
Bs = 
=) - «” 
Pee aa 
ar Px, - 
i ¢ ‘% - 
mi 
s ‘ec 
* i ‘ a r 
! f ase 
‘ 
- 
)  fipegite ‘ i 
Sy peg goa chops es ah aa my 1 Ln 
ca hint ' 
; ' : SA eka yy 
iN ne a, 
We. : “ d 7 
im 
FP oh hy 
eos 
ignr 
’ 
i 
’ 
; 
- 
- 7% 
a 
‘ Ls é 
Os ol J 
4 
= is 


PLATE 106 





B. Live oak uprooted by earthquake, west of Searsville Lake, Per J. C. B 





ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 259 


Menlo Park (H. P. Gage). — At the Catholic Seminary near Menlo Park, a 4-story 
brick building, the upper part of many of the walls fell; towers and chimneys also came 
down; arches were sprung apart, allowing their keystones to drop, catch, and hang. 
There were many cracks in all the walls which remained standing; the capstones above 
the windows on the fourth floor fell out. The chapel behind the northeast side wall was 
thrown in a heap. The I-story brick buildings back of the large one were little 
damaged; a wooden tank was uninjured, altho it was on an 80-foot tower like the 
one in the building which fell. The round power-house chimney (35 feet high) was 
cracked in the middle and the top broken off. A mile nearer Fairoaks Station, a water- 
tank only 12 feet high was thrown down. With this one exception all the tanks on 
this side of the county road appeared to be standing. ' 

(F. Lane.)—A water-tank beside the road, passing north of the cemetery 1.5 miles 
southwest of Menlo Park Station, was thrown down; while one about 0.25 mile nearer 
the station on the same road was left standing. On the second road west of San Francis- 
quito Creek, and running southwest from Menlo Park Station toward the Alameda de © 
las Pulgas, three large trees growing together had been torn apart, and one about 2.5 
feet in diameter had fallen. Water-tanks on the second road west of San Francisquito 
Creek were not thrown down. On the second parallel road west of the Creek, and leading 
southwest from Menlo Park and 1 mile from the station, the roof of a large 3-story 
brick house, which had been recently built, had collapsed, the bricks having been shaken 
from the walls down to the second floor. The Arcade of the Sacred Heart Convent was 
thrown down. (Plate 1014.) 

Fairoaks. — On the road leading southwest from Fairoaks and about a mile south- 
west of that station, a newly completed 1-story bungalow had entirely collapsed. 

(S. Taber.) —At a stable near Fairoaks (about a mile southeast of the junction of the 
Woodside Grade road with the road leading across University Heights) heavy carriages 
and wagons were moved sidewise 6 inches in a direction N. 37° E., but they did not roll 
out on their wheels. These carriages were placed on the northwest side of the barn. 

(H. P. Gage.) Following the road from Fairoaks toward Cooley’s Landing, a house 
with poor underpinning fell over, also the woodshed near it. An engine mounted on 
a platform 2 feet from the ground was not upset. People reported new holes formed 
in the slough near Cooley’s Landing, but their statements were not verified. No damage 
except broken chimneys was noticeable in the vicinity of the Landing, and solidly built 
houses seemed to be intact. One house on a poor foundation was knocked down; while 
the barns, tanks, etc., belonging to it were uninjured. 

(F. Lane.) —South of Menlo Park and east of the Meyer Place on the west side of San 
Francisquito Creek, a crack about 1.5 inches wide ran for 20 feet along the edge of the 
county road parallel to and just above the creek, showing a half-inch vertical displace- 
ment, the lower side lying next to the creek. This crack appears to be due to the start- 
ing of the filled ground of which the road is partly made. The water in the reservoir 
of the Bear Gulch Company, 3.25 miles west of Stanford University, is reported to have 
been thrown about 25 feet beyond the dam on the southeast side of the lake. Water- 
pipes along the road leading from the reservoir toward Menlo Park had been pulled apart. 
The buildings in the neighborhood of the reservoir are of frame, and no great damage 
was done to them, except that the brick chimneys were thrown down. 

Redwood (R. V. Anderson). — The intensity of the earthquake in Redwood City was 
about IX. Many buildings were partially wrecked and the new court-house was com- 
pletely ruined. Over 40 houses in the town were moved upon their foundations, and 
a majority of the houses had the plaster badly cracked. Ninety-four per cent of the 
chimneys fell, and dishes and similar objects were universally thrown down. Along 
the two roads leading from Redwood to Portola, out of 23 big public water-tanks 20 
were thrown down. 


260 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


East of Palo Alto (S. Taber). — On the Embarcadero road, from the railroad crossing 
at Palo Alto toward the Bay of San Francisco, only about half the brick chimneys had 
been thrown down. Plaster on first-floor walls cracked, but it was not injured to any 
extent in the upper stories. Many houses showed little damage to plaster, even on the 
first floor. The tanks of the Palo Alto Water Company (at 1, map No. 22) had not been 
thrown over, but the frame (100 feet high) had slipt on the concrete foundation a maxi- 
mum distance of about 0.5 inch in a direction N. 87° E. The water is reported to have 
slopt out of the reservoir on the east side. A water-tank about 0.5 mile nearer the 
bay (at 2, map No. 22) was standing, as was a brick chimney near it. Damage to houses 
in this section was directly due to high brick chimneys; plaster was sometimes scarcely 
cracked, even on the first floor of houses thus damaged. 

Mayfield to Guth Landing (R. L. Motz). — In the town of Mayfield most of the houses 
are small, 1-story buildings resting on wooden foundations, and many of the chimneys 
were of terra cotta and wired to the roofs. Out of a total of 258 chimneys 183 fell — 
about 70 per cent. A few brick buildings were badly cracked, and the fire-walls were 
all thrown off. The plaster in the small buildings was somewhat cracked, while in the 
larger buildings the damage done to plaster was more marked. The concrete bridge 
over Madera Creek, on the county road 0.5 mile southeast of Mayfield, was not cracked. 
A half mile further southeast along the road, 2 water-tanks and 3 chimneys (2 brick and 
1 cobble-stones and lately built) were standing. A short distance nearer Mountain View 
Landing there were fallen or damaged chimneys (at 4 and 5, map No. 22). 

At Guth Landing a large brick warehouse facing N. 87° E. had its sides cracked, lost 
a few bricks at the top, and had the upper part of its east and west ends knocked out. 
From Guth Landing southward along the road into Mountain View, the effects were 
uniform; chimneys were down with two exceptions, there was little or no damage to 
plaster, and the flow from bored wells had increased. In one case a wind-mill (at 6, 
map No. 22), which had been in use for years to pump water from the well, was no longer 
found necessary, but the artesian water was muddy. 

Mountain View (H. P. Gage). — On the county road between Mayfield and Mountain 
View, concrete bridges were uninjured, water-tanks were left standing, and the smaller 
or more solidly built chimneys uninjured. 

(R. L. Motz.) —In the new town of Mountain View, built mostly in the vicinity of the 
railway station, 6 brick structures, including the Pacific Press and the cannery buildings, 
were seriously injured. Out of 271 chimneys, 206, or 76 per cent, fell; out of 46 large 
water-tanks 20, or 43 per cent, fell. In the Mountain View Cemetery there were 26 
large monuments; of these 11 fell and 7 were shifted, while 13 slab headstones out of 27 
were thrown down. In the village of Old Mountain View 75 per cent of the chimneys 
(31 out of 41) fell, and 332 per cent of the water-tanks (3 out of 9) fell. 

(H. P. Gage.) —On the road leading southwest toward San Antonio Creek from the 
town of Mountain View, the houses showed no uniform damage. At one place south of 
the county road and two miles west of the Mountain View Station, the water-tank 
swayed and threw out several barrels of water during the shock, yet the plaster in the 
house was unhurt and only a few dishes were broken. At the next house, the chimney 
fell. 

At the Weeks poultry ranch 2 chimneys fell, dishes were broken and plaster was 
cracked; but the water-tank was uninjured. 

Two and a half miles southwest of Mountain View Station, beside the road running 
up San Antonio Creek, a water-tank was so badly wrenched that it had to be braced to. 
keep it from falling; another tank, on a side hill west of San Antonio Creek, had col- 
lapsed. ‘The house near the latter, in course of construction, lost an outside chimney. 
Following the road up San Antonio Creek on its southeast side, another house between 
the road and the creek had one chimney cracked and another thrown down; plaster had 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 261 


fallen in the second story, and sewer and underground pipes were broken. Much dam- 
age was also done to the houses on the hill southwest of where this road crosses San 
Antonio Creek. In one of these 3-story houses, the plaster was partly off the first 
floor walls, and windows were broken. The second house was so shaken that it shifted 
several inches upon its foundations. A 1-story cottage close by was little damaged; 
and in the pumping shed, bottles, cans, ete., standing on a narrow shelf did not even 
fall down. The chimneys were thrown down on the ranch house at Hidden Villa, two 
miles northwest of Black Mountain Triangulation Station, but there was no great damage 
otherwise. Big blocks of rock are said to have been shaken loose from the mountain 
and to have rolled down the slopes. One of these rolled into the chicken-house, and 
others broke the water-pipes at several places farther up the gorge. 

On the road running southwest from Mountain View Station toward San Antonio 
Creek and 1.75 miles southwest of the station, a water-tank 8 feet high was thrown down. 
In the village of Mountain View, 0.5 mile southwest of the railway station, one chimney 
on a small house, and projecting 5 feet above the roof, was left standing; while another 
chimney on the same house was thrown down. On the road leading north from Moun- 
tain View, and 0.25 mile from the station, one chimney fell; but another, 1 x 2 x3 feet 
was standing. The latter was braced with iron bolts, however. The plaster in the house 
was cracked, though not very badly, and the foundations were unhurt. 

At the Ynigo ranch, 3 miles northeast of Mountain View Station, the house is large 
and old. Here the chimneys fell, one going down through the roof. The plaster was 
only slightly cracked. Frail sheds and water-tanks 20 feet high on light supports were 
not thrown down, and plumbing in the house was apparently undisturbed. There was 
an artesian well at this place which had, before the shock, flowed only slightly or not at 
all, and a wind-mill was used to raise the water. After the shock, it was found that the 
casing had been shoved up 2 feet, damaging the pump. The flow of water was increased 
and black sand was brought up. Another well at this ranch was unaffected. 

At Jagel Landing there was but little damage. One chimney was unhurt, and another 
was slightly twisted. 

The concrete bridges over Permanente and San Francisquito Creeks showed no new 
cracks. In the low lands northeast of Mountain View, all the chimneys except one at 
the Mascot Gun Club preserve had been thrown down, and water-tanks had fallen except 
where they had been especially well braced. The same was true in the vicinity of Sunny- 
vale. Between Sunnyvale and Lawrence a brick winery was destroyed, and a tank and 
wind-mill were thrown to the ground. On the second east-and-west road directly south 
of Sunnyvale, for a short distance toward Stevens Creek, a few chimneys were left stand- 
ing; but the damage was generally uniform as reported above. 

(F. Lane.)—A 3-story brick wine distillery in the northeast corner of the San Antonio 
grant, 3.5 miles south of Mountain View Station, was totally destroyed by the shock. 
This building was on the side of a hill. A 3-story frame house near it lost its chimney 
and was tipt to one side. A half-mile southof the winery, a water-tank beside the road had 
been destroyed. At the southeast corner of the same grant, a 2-story frame house (Sel- 
linger’s) was thrown from its 4-foot brick foundation and badly damaged. The road in 
front of the house was cracked, but probably on account of the steep slope below the road. 
South of the house, across Stevens Creek, there was a landslide 100 feet in width on the 
steep face of a bluff. 

(S. Taber.) —'The concrete bridge over Stevens Creek on the county road below Moun- 
tain View was not cracked, but at the brick yard, at the junction of the San Jose road 
with the road to Jagel Landing, a high chimney and a pile of brick had fallen over. 

Saratoga to Congress Springs (F. Lane). — At Saratoga some chimneys were knocked 
off, but among those standing was a high chimney built on the side of a 1-story house. 
A wind-mill with a large tank had not been injured and no other damage was apparent. 


262 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


On the Azule Springs road, all the 1-story buildings appeared to be in good condition, 
and few effects of the shock were noticeable. Near the place where five roads fork, one 
mile north of Azule Springs on the road running southeast from the forks, there was a 
6-foot drop on the road caused by a section sinking in a solid piece on a long slope, without 
~ much disturbance in its vicinity. At the cross-roads halfway between Saratoga and West 
Side, the Lincoln school-house, on wooden supports, was thrown from its foundation and 
badly damaged. ‘The tank behind the school-house was standing, as were all the tanks 
on the road from Saratoga to West Side except the one nearest the latter village. Only 
one more effect of the shock was noted in this vicinity; namely, the bridge over Stevens 
Creek, on the road running due east and west from West Side, was rendered unsafe for 
horses by being shoved a foot out of place. 

On the Stevens Creek road, just after leaving the Saratoga road, one house near the 
junction of the two roads was shaken and dishes were broken, but the brick chimney 
was intact. Near the house a crack 2 inches wide showed a downthrow of 2 inches on the 
west side. A vacant house at the next turn, 0.5 mile southeast of Stevens Creek, had lost 
its chimney and leaned with the slope of the hill. Near this house a large area of ground, 
extending for 150 feet, had been torn up in a direction of N. 3° W., and a slide formed 
which almost blocked the road. 

At the Borger place on the Stevens Creek road, the chimney was shaken down; the 
house, which stands on a high but well-built stone foundation, was not damaged otherwise. 
Wine was spilt in the cellar by the force of the shock. Further northwest along this road 
other disturbances were noted with increasing frequency; small cracks crost the road due 
north and south. 

On the northeast side of the creek, 0.25 mile south of the place where a road turns 
northeast from the Stevens Creek road to go up Monte Bello ridge, there was a large 
landslide about 0.5 mile long and terraced from the top of the mountain. 

The short road.which runs northwest along Stevens Creek for a couple of miles beyond 
the junction with the cross-road which connects with the Monte Bello ridge showed an 
exposure of serpentine with cracks running along it N. 3° W. The cracks at the widest 
point measured about one foot. In the serpentine area the ground was badly broken up, 
and in one place it was covered with 3 feet of water. (Observation made April 22-23.) 
Following the road northwest beyond the terminus shown in the map, many cracks were 
seen, due to big landslides. Fallen trees have rendered the road impassable; boulders 
and dead trees still fell occasionally; even while the observer was there a large tree fell 
not 10 feet from him, loosening rocks and soil. 

Just south of the two houses near the southern end of the cross-road leading toward 
the Monte Bello road from the Stevens Creek road, a break ran due east and west; it was 
2 inches wide with a downthrow of 0.25 inch on the west side. Only dishes were broken 
in the house, a 1-story frame structure without chimneys, tho it stands above the big 
slide which was just mentioned. Another crack 4 inches wide was found in the road above 
the house. 

The village of Congress Springs had not been shaken very badly. All water-pipes 
and tanks were intact and very little timber seemed to have fallen. The car tracks on 
the curve near the path to the spring had been thrown over toward the bank for about 20 
feet of the curve, a 4-inch displacement resulting. The 2-story stone building of the 
Saratoga Wine Company was partially thrown down, and the side nearest the road had to 
be propt up to keep it from falling.. At this point several cracks were noticed in the loose 
alluvial material of the road, almost at right angles to each other. 

Stanford University to Portola and Woodside (S. Taber). — Going southwest from 
Stanford University along the road leading up San Francisquito Creek (at 8, map No. 22), 
- on the banks of the creek many dead limbs were broken from trees, and a dead oak 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 263 


2 feet in diameter was broken off about 20 feet from the ground. But little damage was 
done at a house a short distance farther west. On the north side of the creek (at 9, map 
No. 22), the 12-inch cast-iron pipe of the Stanford University water-main, buried about 
3 feet deep, was cracked, allowing the water to spurt 20 feet into the air. 

Beside the road just west of Searsville reservoir, a living white oak 6 feet in diameter 
was uprooted by the jerk of the earthquake shock. (Plate 106a.) At the Searsville 
dam the waste way is 45 feet wide. The water running over the spillway was 4 inches 
deep before the earthquake, but afterward it increased to 5 inches; more water was also 
noticed in the creek that empties into the lake. 

The Preston residence, about 0.5 mile south of Searsville Lake, lost its chimneys. 
Along the road leading from Searsville Lake southeast thru Portola, the water-tanks were 
all thrown down, except one near the junction of the Portola road with the Alpine road. 

The bridge at the north end of the village of Portola had the ends thrust together so that 
the planks forming its floor were thrown out of place. In Portola, brick chimneys were 
all down and water-pipes were broken. The Portola store was thrown off its foundation. 
The Catholic Church in the village is a frame building that stood upon an underpinning 
of posts about 3 feet high. This building was thrown bodily about 2 feet toward the north, 
apparently thrust over by the underpinning when it gave way. The Portola school- 
house was also thrown from its foundation, which was about 3 feet above the ground. 
Two small dwelling-houses southeast of the school-house and on the south side of the 
road were thrown from their foundations. 

Following the Portola road from Portola toward Woodside, the houses showed con- 
siderable damage, with chimneys down. The water-tank at the fork of the road in front 
of Mr. Preston’s house was thrown down, and the big tank at the fork of the road, at the 
site of the old village of Searsville, was also thrown down. The white oaks in the field 
north of the road had also many large branches broken off by the shock. A shanty 
between the 2 bridges (at 11, map No. 22) was down flat; and in a few cases the under- 
pinning of houses had given way, the houses having settled in consequence. Small trees 
were overturned and fences broken. A large live oak had its top broken off about 20 feet 
from the ground (at 12, map No. 22); at the place of fracture the tree is about: 3 feet in 
diameter. ; 

Taking the western road past Newman’s, which is at the place where this road crosses 
Bear Creek, from Searsville Lake to Woodside, two especially well-built water-tanks 
beside the road, tho well shaken on their foundations, did not fall. On the south side of 
the road, about 0.25 mile southeast of Mr. Folger’s, a large live oak was torn up by the 
roots (plate 1068), while several eucalyptus trees had branches jerked off. A strongly 
built 1-story house just below (18, map No. 22), and within 400 feet of the fault-line, 
lost all of its chimneys, but the plaster was only slightly cracked. Beds and other fur- 
niture in the house were jerked in directions parallel to the fault-line. A small bed stand- 
ing in the northwest corner of a room was not moved, but a larger bed near the center of 
the same room was moved several feet. A water-tank a short distance northwest of the 
house, new and strongly built, about 15 feet above the ground, had nearly all of the water 
spilt out of it. An eye-witness says that the water was thrown high up on the northwest 
and southeast sides. The water-pipe running from the house to the pump was bent in a 
curve toward the northwest, and where it entered the pump-house, the boards were broken 
on the southeast side of the pipe. The other pipe (also 4 inches in diameter) had the 
threads stript off at a joint, and the ends of the pipe pulled apart for a distance of 2.5 to 
3 inches. The pipe was new and buried a few inches below the surface of the ground. 
A large oak tree standing 200 feet or so from the house had large limbs broken off by 
the shock. At the Folger place, between Newman’s and Portola, the chimneys were all 
thrown down. 


264 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


On the west side of Bear Creek and north of the road along the foot of the mountain 
near Woodside, a 1-story sandstone house had its south wall thrown down, and was 
otherwise badly damaged. About 50 feet of stone wall, laid with mortar, along the side 
of the road, 3 feet high and 1.5 feet wide, was thrown down. A tank at the cross-roads 
in Woodside was left standing. The upper part of a brick winery 14 stories high (at 
26, map No. 22) was demolished, the roof being split down the middle and smashed to 
pieces. A house 14 stories high (at 14, map No. 22) was thrown toward the southeast, 
the underpinning giving way in front. The house was badly damaged. Water in a large 
tank near the house spilt out on the southeast and northwest sides. 

At the very end of the short, crooked road mapped as running northwest from the village 
of Woodside, there was a well-built 1-story frame house, of which the brick chimney 
had been thrown down; the plaster of the house was only slightly cracked. Near this 
a large water-tank was thrown over; another remained standing but had the shingles 
knocked off the roof on the northwest side by the force of the water dashing up against it. 
The old adobe house at the cross-roads in the village of Woodside was thrown down, 
the posts and supports left standing leaned at a considerable angle toward the northwest. 

A large frame house (Mr. Josselyn’s residence), north of the road and close to West 
Union Creek, was demolished; while another on the opposite side of the road, and just 
south of the bridge, was not badly damaged. The concrete bridge over West Union Creek, 
1 mile south of the point (14, map No. 22), showed a few small cracks. From this point 
on up King’s Mountain road, as far as the summit, there were no cracks nor landslides. 

Page Mill and Alpine roads (8S. Taber). — All brick chimneys along the upper part of 
this road were thrown down. At the Clarita Winery crockery was broken and milk 
spilt from pans. On the road from Clarita Vineyard to the Allen place (at 18, map. No. 
22), several small cracks 0.25 to 0.5 inch across ran east and west; numerous cracks 
intersected (near 18, map No. 22) in various directions, while some large ones running 
parallel to the contour lines were probably due to earth slipping. Judge Allen’s in the 
valley, and several smaller houses, were thrown from their foundations and otherwise 
badly damaged. 

Following the Alpine road up Corde Madera Creek, cracks were common on the outside 
or filled portion of the road, and these were generally parallel with the embankment. 
The steep southern slope of the ridge just north of the Alpine road, along its lower course, 
was favorable to landslips. At many places huge masses of rock had been thrown down 
from these steep bluffs into the road, completely blocking it up. On the south side of the 
creek the slopes were not favorable to landslips, but there were several of them; and at 
one point, about a mile from the summit of the ridge where this road enters the Page Mill 
road, one slide carried away the entire roadbed for a distance of about 300 feet. 

(H. P. Gage.) — Following the Page Mill road westward from Black Mountain toward 
Langley Hill, a 1,000 gallon tank was undisturbed, but 3 live-oaks near by were uprooted, 
one of them being a large tree with a 12-foot base. These trees were in a rather dry soil, 
yet none of a grove of trees growing in moist soil was overturned. Farther west up the 
road which loops toward Langley Hill, a big crack running east and west, caused by a 
slide, showed a drop of 8 inches on the north side; and from here on down to the Alpine 
road the road was badly cut up with slides, but was not impassable. On the steep grade 
of Langley Hill a slide had moved 80 fect. At the ranch houses there was little damage 
done by the shaking save sometimes a fallen chimney or a few broken dishes. At one 
ranch the people reported that cows were much frightened during the shock. 

(I. Lane.) —Along the ridge road southwest of Stevens Creek, separating Santa Clara 
and Santa Cruz Counties, there were some cracks due to landslides. Sandstone blocks, 
some of them 6 feet in diameter, had rolled down the hills toward the creek. People at 
the houses along this road stated that the shaking had been severe, with loss of a few 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 265 


chimneys but very little destruction otherwise. No evidence of cracks could be found 
upon the side road. At a house situated at the junction of four roads about 3 miles west 
of Congress Springs, no damage was reported, tho the inhabitants were up at the begin- 
ning of the shake and say that it was accompanied by considerable rumbling and that the 
shocks which followed were preceded by a sound like a blast. 

King’s Mountain down Purisima Creek (8S. Taber). — At King’s Mountain House, brick 
chimneys were knocked down and some dishes were broken, but no damage was done to 
the house. Cream was spilt from the milk pans on the southwest side. On the Cahill 
Ridge road leading northwest from King’s along the crest of the ridge, little damage was 
noticeable. An old woodshed was thrown down (at 21, map No. 22), and about a mile 
farther on the top was broken from a large redwood tree about 75 or 100 feet from the 
ground (at 22, map No. 22). 

Following the trail from King’s Mountain House down Purisima Creek, a large slide on 
the northeast side of the creek had filled the road to a width of about 100 feet (at 23, 
map No. 22). The buildings at Hatch’s Mill, just below (24, map No. 22) were not dam- 
aged, but a little farther down several cracks were found, one 8 inches wide and running 
S. 23° E. On the northeast side of the creek, just below Borden’s Mill, a big slide had 
dammed the creek to a depth of 25 or 30 feet (at 25, map No. 22). The slide was between 
0.25 and 0.5 mile long. The buildings at the mill showed no damage, but a bridge just 
above the mill was crusht by a slide from the south side of the creek. 

Bear Creek (H. P. Gage). — Between Redwood City and Woodside, all of the public 
water-tanks were thrown down or had to be rebuilt. On the Bear Creek road, southwest 
of Woodside, there were many cracks caused by landslips down steep banks. The tops 
of 2 partly decayed trees, one a redwood and the other a spruce, had been broken off 
where the diameter was 2 feet. Near where the first trail branches to the right from 
this road, an old oven built of clay and stone, 4 feet high, was cracked, and an old barn 
was badly damaged. At the point where the road itself becomes a trail there is a log 
cabin, probably used as a summer camp. This cabin was locked and had apparently 
remained undisturbed since the earthquake. The floor is about 6 feet above the level of 
the ground. Table, benches, chairs, and all the bottles and utensils, except a coffee pot, 
were overturned. The table was solidly built and measured 4 by 8 feet. About a mile 
east of this cabin, at the end of another trail, was a 1-story frame house; a bed on the 
_ first floor was moved by the shock 8 feet to the middle of the room, tables and chairs 
were displaced, and dishes were broken. A house and dairy between this place and the 
road were moved on their foundations, and water was spilt out of pails from northeast to 
southwest. Tops of spruce trees were broken by the shock. Four miles farther south- 
west, along the trail toward the San Gregorio road, people reported that all the stoves 
on the first floor of their houses were overturned during the earthquake, with the ex- 
ception of a kitchen range which was twisted around 6 inches. Their dishes were also 
broken. Just south of the junction of this trail with the San Gregorio road, a 2-story 
house had been shifted on its underpinning and some plaster was broken. A water- 
tank 20 feet high fell at this point. 

Half Moon Bay, Purisima and San Gregorio (S. Taber). — Following the road along 
Pilarcitos Creek toward Half Moon Bay, many cracks and slides were found on the ocean 
side of the ridge, but few on the east side. All of these seemed due to slipping of the earth. 
At one place there had been such a large slide that big blocks of sandstone had fallen 
down into the road. Here and there along the road big cracks had opened, parallel with 
the road and the creek where the slope is very steep, and promising to make the road 
impassable by landslides, should a heavy rain come. 





Tra. Lane adds: ‘‘ While I was there, however, we had a slight shock and I noticed neither blast 
nor noise.” 


266 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


Just north of the bridge over Pilarcitos Creek, north of the town of Half Moon Bay, an 
adobe house west of the road was thrown down by the earthquake, killing 3 people (at 30, 
map No. 22). The concrete bridge was badly cracked, as were the approaches at both 
ends. Just south of the bridge, several small cracks in the low ground west of the road 
permitted water to spout up, bringing sand with it. In the town of Half Moon Bay 
many buildings were badly damaged, some old frame houses and the brick bank build- 
ing being flat, while the upper half of a 2-story brick structure was demolished. The 
Mosconi Hotel, a 2-story frame building, had plaster shaken from the side walls of the 
first floor only, while the ceilings of these rooms were not cracked. 

In Half Moon Bay it was reported that there was no evidence of any change of level 
along the coast. The streams on the west side of the mountains were said to have 
doubled in volume. The road along the coast from Half Moon Bay to San Gregorio 
showed comparatively few traces of the earthquake. The concrete bridge over Canada 
Verde (at 31, map No. 22) was slightly cracked, and 0.5 mile farther south a water-tank 
lay flat across the road. 

At Purisima the chimneys were all down, and crockery was broken. The intensity 
of the shock was apparently less at Purisima than at Half Moon Bay. According to 
various reports, a crack east of the road below Purisima, due to a landslip, extended for 
about 1,000 feet nearly north and south; and an earthslide on the side of a hill a mile or 
more farther south was about 100 yards long and 80 feet across. 

At San Gregorio very little damage was done. The hotel lost only a little plaster and 
a few dishes. Turning eastward on the road along San Gregorio Creek, traces were 
found of increasing intensity. A mile from the town of San Gregorio, a water-tank 20 
feet high was still standing, while a couple of miles farther east the creek was dammed up 
to a depth of 6 feet by a slide from its southeast bank (at 32, map No. 22), and all chim- 
neys were down. Miss L. E. Bell reports that near Bellville a small alkali flat was raised 
about 3 feet. There was a landslide into the road for a distance of 300 feet, the height 
of the slide being 100 feet (84, map No. 22). Chimneys and tanks all thru the valley 
were thrown down. 

(G. A. Waring.) —Of the 2 stores at San Gregorio, the one in the bottom-land suffered 
most, nearly all the shelf goods being thrown down. Cracks from 12 to 18 inches wide 
appeared in the cultivated bottom-land, and a water-tank was shifted on its platform 8 
inches northward. In the Lobitos saloon a slot machine was hurled to the floor, and 
nearly all the bottles on a shelf running east and west were thrown off. Small cracks 
appeared in the ground at Lobitos, and a small slide occurred in the road 0.25 mile up the 
stream. 

La Honda (H. P. Gage). — The inhabitants say that after the shock the creek rose 
about 4 inches and became muddy. At the hotel, plaster fell from first floor walls; the 
rest were little damaged. The plaster had already been cracked, however, by raising the 
house. Lamps were all shaken off the tables, and all the chimneys were down. Water 
spilt from the horse-trough in a northeast-southwest direction. 

Near the Wecks ranch house, between La Honda and the summit of the ridge on the 
road leading to Redwood, an inconspicuous crack was noticed running east. It was 
about 2 inches wide, with no vertical movement evident. The north side of the crack, 
however, had moved fully 3 feet eastward. The crack simply marks a big slide which 
has been slipping for years, and which descended 3 feet during the earthquake. The 
Weeks house, a strongly-built frame structure, 25 stories high, was badly damaged. <A 
large outside chimney fell thru the roof to the first floor, and the plaster was fairly stript 
from the lower rooms and somewhat cracked upstairs. The sliding doors downstairs 
were shaken off their tracks, several windows were broken, the front door was cracked, 
and many of the door jambs were broken. The heavily built barn near the house was 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 267 


badly strained. The water in the reservoir was spilt from northeast to southwest. 
In an old house near the summit the stove was not moved at all, but the chimney built 
40 years ago fell. 

(S. Taber.) —For some distance on the west side of the summit sandstone blocks had 
been cracked off and scattered across the road. From the summit of the ridge to the 
Portola Valley, the only effects noted were the wreck of a ramshackle old barn and a 
3-inch crack across the road (at 36, map No. 22), probably due to settling. 

Congress Springs to Boulder Creek (B. Bryan). — From Congress Springs, following the 
road that passes along the valley, about a mile east of the Castle Rock Ridge, in a south- 
easterly direction toward the reservoir of the San Jose Water Company, evidences were 
found that the earthquake had an intensity of over IX. The walls of a stone barn had 
been thrown down, 1,000-gallon wine-tanks in a cellar had been shifted, and people in 
the houses were thrown down while trying to get outdoors at the time of the shock. In 
a house close by, at the south end of the dam, the first floor plaster fell. Poorly built 
foundations fell. Southeast of the reservoir the chimneys and water-tanks were down. 
Two water-tanks at and near the bend of the road (at 37, map No. 22), were standing, 
but 0.5 mile northwest of this place a water-tank had fallen. The water in the reservoir 
(at 38, map No. 22) had overflowed the 3-foot banks, but the water-tanks were standing. 
A short distance down the road, to the northeast of the reservoir, another tank was 
standing. A house 0.75 mile east of this reservoir was badly shaken, with loss of plaster 
and chimney. In the section a mile east of the fault-line (at 39, map No. 22) the shock 
was weaker. All the chimneys on cottages were standing as far as could be seen, as well 
as all the water-tanks. The bridges 0.5 mile southeast of the reservoir were considerably 
shaken. Cracks seemingly continuous in the direction of the fault-line ran thru the area 
0.75 mile east of the fault-line. Two-story frame houses along the fault line 1 mile south- 
east of the reservoir mentioned were so damaged within that people were living outdoors; 
yet the shake had not broken a 6-inch flag pole on a 2-story frame house. A large 
redwood tree had been shaken down (near 40, map No. 22); the house near it had its 
chimney fractured down to the fireplace, and the stove and piano were thrown across the 
room. The water-pipes here were badly displaced and broken. ‘The intensity was 
greatly diminished, however, near 41, map No. 22; chimneys did not fall, tho fractured; 
clocks were stopt; little rock was thrown down from a vertical outside wall 15 feet high. 

On Deer Creek a large landslide started from near Grizzly Rock and slid westward, but 
changed its direction 60° or more farther down toward the creek. The mill in the creek 
bottom below the slide was partly buried, and one man was killed. It is 500 feet from 
the mill in the gulch to the top, at the point where the slide started. The slide covered 
about 25 acres of ground, and destroyed a lot of virgin timber from 3 to 10 feet in diam- 
eter. The slide material, which is 300 feet deep, is composed of soil, clay, and shale. 

The shock could not have been very strong at 42, map No. 22. The houses stand on 
posts 10 to 15 feet high, but were not moved noticeably. Furniture facing most nearly 
north and south was thrown down, but not when facing in other directions. The inhabit- 
ants were badly frightened and ran outdoors without waiting to dress. On Bear Creek 
(at 43, map No. 22) a smaller slide had moved a few hundred feet, buried a hut, and 
killed one man. According to reports of men in this region, only a minute elapsed after 
the beginning of the earthquake before the slide was over. Down in the valley no cracks 
or other evidence of violent disturbance could be seen. 

Farther southwest down Bear Creek, about 1.5 miles from the village of Boulder Creek, 
were evidences of a less severe shock. A chimney on a I-story house did not fall, tho 
the furniture in the house was thrown down. ‘Trees were violently shaken. A mile 
northeast of Boulder Creek a chimney on a 2-story house was down, but no buildings 
were moved or broken. 


268 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


In the town of Boulder Creek, all chimneys were down except those on some 1-story 
cottages; these were cracked, however. People generally ran out-of-doors, but were not 
as a rule very badly frightened; some even stayed inside until they had drest. Water- 
pipes were not broken, but some plaster had fallen, and plaster was cracked everywhere. 

Mr. Bloom, owner of a sawmill at the edge of the Big Basin, reports that the shock was 
less severe in the Big Basin region than at Boulder Creek; that there were no landslides 
on the road between the two places; and that, tho he had been nearly to the summit on 
the day of the earthquake, he had seen only one crack where the earth had started to slide. 

(R. Collom.)— At Boulder Creek, on the east side of the stream, a small hill of about 
150 feet elevation rises rather abruptly. Its sides are thickly covered with small trees 
and brush. Near the top, a large portion of the surface soil had been shaken loose, and 
had slid to the level of the creek, carrying trees with it. 

At Ben Lomond no fissures nor other such evidences of the earthquake were to be seen. 
Inquiry showed this condition to continue in the country about the town. Broken 
chimneys were the only evidence. The inhabitants of Ben Lomond report several slight 
shocks during the night of April 21-22, 1906. 

(B. Bryan.) —Going north from the village of Boulder Creek along the San Lorenzo 
River, only small wooden houses were seen, all with chimneys standing. There were 
few evidences of the force of the shock, except fallen redwood trees. Three dead red- 
woods had been snapt off from 30 to 50 feet above the ground; and farther on two more 
were noticed, one having broken and the other having been uprooted. A man who was 
at the sawmill, 8 miles north of Boulder Creek, at the time of the earthquake, stated that 
a few trees were torn up by the roots. Cordwood had been thrown down in several in- 
stances along here. A small landslide had moved across the road (at 44, map No. 22), 
which 20 men spent one and a half days clearing away. In the gulch the tops of a 
number of redwood trees had been broken off from 50 to 100 feet from the ground, the 
diameters at the point of fracture measuring from 10 to 14 inches. Up the road to the 
summit of Castle Rock Ridge no slides nor cracks were observed. 

On Boulder Creek, coming southeast down the China Grade, the shock was strong, but 
apparently not so severe as along the San Lorenzo River. The people were badly fright- 
ened by the shaking, however. One man reported that no redwood trees fell and that 
only a few dead limbs were broken off. Near the junction of the first road leading from 
Boulder Creek into the Big Basin, an old landslide which covered about 2 or 3 acres, 
dating back to the previous winter, had been widened by the shock and its direction had 
changed. Only a couple of hundred yards farther down the road, some stacks of smooth 
split redwood logs (cordwood size) had not been shaken down. 

A small earthslide had started (at 45, map No. 22), and a crack, perhaps due to the 
same slide, was noticed. For the next mile or so southeast, there was a considerable 
amount of cordwood along the road, none of which was disarranged by the shock; and 
no trees nor dead limbs had fallen. In the houses between this place (45, map No. 22) 
and the sawmill (at 46, map No. 22), the evidences of damage were more serious. At 
this first place visited no damage was done; people were awakened but did not get up; 
no trees nor limbs had fallen. At the next place, 1 mile southeast, people ran from the 
house during the shake and attempted to remove a sick man. Small objects were thrown 
down and a pendulum clock was stopt. At the house just southeast of the mill, the inside 
furniture was overturned, the stove moved, and the terra-cotta chimney split and fell; 
while branches were broken from redwood trees near the house. At the mill the same 
effects were noted, and others as well; tops of live trees, from 6 to 8 inches in diameter 
at the fracture, were broken off. From the point (46, map No. 22) down to the road 
leading to Bloom’s Mill, 1 mile south of the point (45, map No. 22), the intensity 
seemed to have been less. A water-tank beside the road was quite unhurt; houses were 





(69 4 -10M—7-23) 








ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 269 


not badly shaken; and only small objects — cooking utensils, etc. — were thrown down. 
At an old mill 2 miles southwest, however, a clock had been thrown upon the floor and 
broken at 5" 11" a.m. Half of the piled lumber had been disarranged, and the water- 
tank, built on a frame 15 feet high, was shaken so that it fell the next Monday night. 

Ben Lomond Mountain to the Coast (B. Bryan). — At the junction of the Ben Lomond 
Mountain road (47, map No. 22), the house was empty, but there was no noticeable dis- 
turbance in the sheds or neighboring trees, tho a few hundred yards south a few dead 
limbs had been recently broken from the redwoods and one or two dead trees had fallen. 
Some other trees were so loosened at their roots that they have fallen since the earthquake. 
At the Ben Lomond Wine Company, a place 2 miles southeast of the junction of the roads 
(at 47, map No. 22), a well-built cottage had 2 tall chimneys still standing. People did 
not leave the house during the earthquake. Leaving the Boulder Creek road, and cross- 
ing Ben Lomond Mountain by the Eagle Rock road, the damage appears to consist largely 
of fallen chimneys. Small objects, such as fruit jars, china, etc., were thrown down, but 
only from shelves against north and south walls. People left their houses, but were not 
much alarmed. 

No evidences of a violent shaking were to be found on the trail following southwest 
down Big Creek, either in trees or buildings, except where a small, half-decayed shack had 
been thrown out of plumb and a set of shelves overturned in another cabin. A table near 
these shelves was unmoved, and the bottles on top of it were standing. At the dam on 
Big Creek (at 48, map No. 22), no harm had been done, nor was any damage visible in 
3 old shacks just below the dam. A half mile from this point cracks caused by slides 
were noticed on a very steep bank. Slight damage was done to the flume (at 49, map 
No. 22), which 3 men repaired in half aday. A few objects were thrown down in dwellings 
hereabouts. Near the junction of Scott and Big Creeks, a light terra-cotta chimney did 
not fall, but milk was spilt from pans at this place. 

(H. W. Bell.)—At a house 1 mile southeast of the junction of the east and west forks 
of Waddell’s Creek, a brick chimney was thrown down. Near a deserted mill at the north- 
end of Ben Lomond Mountain, a small landslide had carried trees and brush down to the 
creek, and tall trees had fallen along the road. At a new mill a short distance from the 
old one, about a mile northwest of Eagle Rock, it was reported that the shock was dis- 
tinctly felt, but no damage was done. Dishes even stayed on the shelves. A steep bank 
beside the road showed small cracks, which could apparently have been easily made in the 
loose soil. 

(G. A. Waring.) —At Swanton it was reported that a distinct noise, as of a team cross- 
ing a bridge to the northwest, had been heard preceding each shock. Dishes on a shelf 
running northeast and southwest were thrown off, while those on a shelf standing at 
right angles to these were unhurt. 

(B. Bryan.) —At the school-house (50, map No. 22) the globes were overturned by 
the shock. The teacher said that she had heard from the people at the end of the trail 
just above, leading northwest toward Swanton, that the shaking had overturned only 
a few glasses, and that their pendulum clock did not even stop. At the next place, 
0.5 mile southeast of the school-house, no damage was done, and the inhabitants were 
not disturbed enough to run outdoors. . In the little settlement at El Jarro Point, the 
shock was so light that a small chimney with a terra-cotta top, making a height of 7 
feet above the roof, did not fall; nor were similar terra-cotta chimneys on 2-story 
buildings thrown down, tho projecting from 3 to 4 feet. Glasses and bottles remained 
on the shelves in a bar-room. 

At the lime-kilns (51, map No. 22) the shock had apparently been more severe, for 
tho no cracks were found in the kilns themselves, people ran from houses, small objects 
were thrown to the floor, and piles of cordwood were overturned. 


270 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


(G. A. Waring.) —At the San Vicente lime-quarry, the intensity was found to have 
been considerably higher in the bottom of the canyon. A cow in the yard could not 
keep her feet, men could not walk to the door of the cook-house, and milk and water 
were nearly all thrown from the pans and kettles. Little or no damage was done to 
the buildings or furnaces, and cordwood on the steep slopes was not thrown down. 

At Coast there was little sign of destruction by the earthquake, and nothing could 
be learned. At Bonnie Doon, tho the shock was appreciable, no clocks were reported 
stopt and nothing was thrown from shelves. 

(B. Bryan.) —On the road thru Bonnie Doon the shock was uniformly light; chimneys 
were unharmed, plaster was intact, clocks did not stop, and even the milk had not spilt 
from the pans. People did not run outdoors. A top-heavy and rickety pigeon-house 
did not fall over, tho shaken considerably. 

Down Laguna Creek to Coast, and up the trail east of Coja Creek to the asphalt beds, 
similar effects were noted. Near the latter spot, however, the shock appeared to have 
been somewhat stronger; small objects had fallen, milk spilt, and even one chimney 
was thrown down, while people were frightened enough to get out of the buildings. 

From the asphalt beds as far east as the point 52, map No. 22, the observer found 
no one to question; but the shake had been so moderate as to leave no visible signs 
except where some cordwood had broken its end-stakes and rolled down at the ends. 
At the houses just south of this point, chimneys and plaster of 2-story structures 
were not damaged; only lamp-chimneys and such articles fell and broke. It was re- 
ported that at one house in the valley fruit-cans had been thrown from shelves. 

(R. Collom.)—At the Wilder dairy, on the Santa Cruz-Pescadero road, 2 miles west 
of Santa Cruz near Meder Creek, the damage done by the shock was in the form of broken 
chimneys and cracked plaster in the houses. On the road 0.5 mile west of the dairy, 
the force of the shock broke an 8-inch water main. 

A general examination of the country along the coast, as opened up by the Pescadero 
stage road, shows the damage in these parts to be confined mostly to broken chimneys 
and cracked plaster in the houses. Only in the case of buildings with very poor founda- 
tions was any of the superstructure destroyed. 

(G. A. Waring.) —At Wilder’s dairy it was said that the shock seemed to come south- 
ward down the gulch, preceded by a rumbling from the same direction. Other places 
on the terrace-land near the shore west of Santa Cruz were not so badly shaken. 

Santa Cruz (B. Bryan). — Entering the city of Santa Cruz from the west, the first 
chimneys down were only about 0.5 mile from the San Lorenzo River, increasing in 
number as one came into the town; yet many of the better-built chimneys, even on 
2-story and 3-story buildings, were not thrown down. In the eastern part of Santa 
Cruz, some chimneys on both 1-story and 2-story houses fell, and some stood. In some 
cases plaster was cracked, but in no case where enquiry was made had much fallen. 
Some small objects fell in every instance. 

(R. Collom.)—The shock was strong, but no lives were lost. The court-house roofs 
and towers were wrecked, many brick chimneys were down, and communication with 
other towns was entirely cut off by the breaking of telephone and telegraph wires. Many 
buildings had their walls shaken down. 

At the north end of the bridge crossing the San Lorenzo River, at Third Street, there 
were 4 fissures running practically parallel and almost due east and west. These fissures 
are about 700 yards in length, and vary in width from 2 to 8 inches. They run thru an 
apple orchard and are in sandy soil, the softness of the land near the river-bed being 
apparently responsible for their presence. The river at this place runs about east. 

In going thru the town of Santa Cruz in the direction of Boulder Creek, a fissure at 
the intersection of Bulkhead and River Streets was noticed. This fissure was about 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 271 


1.5 inches wide and ran east and west. The 90-foot brick smoke-stack of the San Lo- 
renzo tannery, which is about 18 feet in diameter at the base, was unharmed by the shock. 
It is said that as far as was observed, there was no change in the appearance of the sea- 
level at Santa Cruz; nor was there any damage done by the sea, nor any unusually large 
waves at the time of the shock. 

At the Southern Pacific bridge, crossing the San Lorenzo River, there is a network 
of fissures varying from 2 to 15 inches in width, running thru the sandy soil. The direc- 
tion of the main fissures is east and west, and they are on the south side of the river, 
which is nearest the bay. The ground has settled about 10 inches from the abutments 
and piers of the bridge. The depth of the fissures was indeterminable, as they had 
filled with sand. At Santa Cruz the inhabitants reported that near Olive Springs, 12 
miles north of Santa Cruz, a landslide demolished Loma Prieta Mill and killed 9 men. 

(G. A. Waring.)—The city of Santa Cruz furnishes excellent evidence of the effect 
of soil formation on the intensity of the earthquake shock. On the high ground in 
Garfield Park, and also in the northwest part of the city, only about one-fourth of the 
chimneys fell and a little plastering was cracked; while in the lower ground near the 
business section several brick and stone buildings were partly shaken down. The San 
Lorenzo River was churned into foam, the banks cracking and settling several inches; 
and sand, said to have come from a depth of 100 feet, was forced up in several places. 
The bed of the river is also said to have sunk several inches, and the current to be slower 
than before. A 6-inch water-main, running east and west across the river at the covered 
bridge, was broken at each end of the bridge and moved 5.5 inches eastward. A man 
out of doors, facing south, was thrown east, then in the opposite direction. A eucalyp- 
tus grove south of him swayed violently east and west. 

Along the beach the shock seems to have been less severe. The running engines of 
the power-plant at the Casino were unaffected. ‘Things were thrown mostly from the 
west wall in a curio store on the beach. The wharfinger says he heard a rumble before 
the shock, coming from the southeastward; and saw the seismic wave traveling shore- 
ward, causing a great rattling and crashing when it struck the town. Two distinct periods 
of vibration were felt, the latter being the harder. There was very little surf, the water 
looking like that in a tub when jarred. A safe in the wharf office rolled 3 feet eastward 
against the counter, then back again hard against the wall. The wharf, extending 
southeast, seemed to pitch lengthwise. Mr. W. R. Springer, jeweler, reports that out _ 
of 25 clocks repaired by him, which had been injured by the shock, 20 had their pen- 
dulums thrown off. 

At the Santa Cruz light-house, a noise as of a wagon crossing a bridge preceded 
every quake. The motion seemed vertical as well as horizontal, for the glass globe over 
the lamp was jarred out and broken. In the curio-store at Vue de |’Eau, nothing on 
the lower floor was disturbed and only a few vases and pieces of bric-4-brac on the second 
floor were displaced. The shock seemed to come from the south. No effect on the surf 
was noticed. 

(R. Collom.)—Going north from Santa Cruz, a small fissure ran northwest and south- 
east on the Boulder Creek road, about 0.75 mile northwest of the California Powder 
Works. Along the lower end of this road were several small and unimportant land- 
slides. In general, the shock in this region does not seem to have been as severe as it 
was farther north. 

Road into Scott Valley (B. Bryan). — Following the road from Santa Cruz into Scott 
Valley, at a summer hotel the chimneys were cracked all the way down, but were still 
standing; light objects on the first floor were moved, and bureaus on the second floor 
slid a foot or so. A 1-story frame house (at 53, map No. 22) was moved 4 feet or 
more, and a piano and other heavy objects were shoved across the room. The damage 


272 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


to the house was so serious that it was being torn down at the time of observation. A 
4,000-gallon tank (at 54, map No. 22) was moved and burst open, letting out 2,000 gal- 
lons of water. At the house nearest it, the chimneys were cracked, but nothing inside 
had been disturbed except some bottles, and no plaster was cracked. Houses in Scott 
Valley had about this same amount of damage; chimneys were sometimes cracked but 
were still standing, and plaster did not fall. 

Miss Finette Locke, of Scott Valley, reports that a man was thrown to the ground by 
the shock, and when he arose could not walk because of the earth’s motion. The vibra- 
tion was northeast-southwest. Everybody was awakened; all clocks were stopt; plas- 
tering was extensively cracked; and all chimneys were broken. About a mile north 
some chimneys fell, and in one house 4 dozen jars of fruit were thrown from shelves. 
Landslides and cracks are reported between Scott Valley and Felton, and the dam across 
a small lake was cracked. A statuette and a vase fell to the northeast. The largest 
chimney moved 2 inches to the northeast. The entire width of the road to the south- 
west of the small lake was splasht with water thrown out of the lake. Long billows 
on the lake extended northwest and southeast. In an 8-foot trough orientated east and 
west water was caused to sway back and forth, but not parallel to the sides of the trough. 
A neighbor who was awake heard a roaring noise in the northeast. Much milk and 
cream was thrown out of pans. 

Going from Scott Valley toward the town of Felton, the shock appeared to grow con- 
stantly lighter; some people did not even get out of bed. 

Felton. — In this village the shock was apparently lighter than at either Boulder Creek 
or Ben Lomond. At Zayante, some cordwood and some finer split wood, piled 8 feet 
high, was not shaken down, tho some of it was said to have been disturbed. 

(R. Collom.)—The shock was only moderately strong. The damage consisted of 
the destruction of brick chimneys. Earthquake effects at this point are shown only 
by the damage to artificial structures. 

Pescadero to Butano Creek (H. W. Bell). —In the town of Pescadero the shock was 
heavy; all but 3 brick chimneys fell, and but few buildings were otherwise damaged. 
Plastering was knocked from the walls in most of the houses, and church bells were 
rung. All the water-tanks observed were still standing, and none of the churches had 
lost their steeples, tho one church was cracked open. Cracks were visible in the streets. 
One man walking eastward along the road near Pescadero was thrown flat on his chest 
by the first shock, but jumped up and braced himself in this direction, and was then 
thrown southward. Cracks in the road also appeared, and dust spurted up. Several 
people were nauseated by the motion and some said that a noise as of a wind preceded 
the shock. ‘ 

Going eastward from Pescadero, a small crack 30 feet long, with an east and west 
strike, was observed. In an orchard near by there were several cracks, the widest one 
measuring 8 inches, with a vertical displacement of 1 foot. About 2 miles east of the 
town, on the north bank of Pescadero Creek, a landslide in the shape of a half-moon, 
its axis lying N. 23° W., had slipt down toward the bed of the stream. The greatest 
vertical displacement at the top of the slide was 15 feet; the distance from its apex to 
the road about 85 feet; and the span from end to end along the road about 220 feet. No 
solid rock was exposed by the slide. The road had dropt 6 feet at the south end, and 
8 feet at the north. Only a few cracks appeared on the surface of the part which had 
slipt. The creek lying directly below the road had apparently received very little soil 
from the landslide. 

Along the stretch of road between this slide and the town of Pescadero, there were 
few cracks in the road and the houses were in good condition. The only brick chimney 
seen was down. The intensity was apparently the same as in the village, and continued 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 273 


the same along the road leading southeast toward Butano Creek. A 1-inch crack at 
the first fork of the road a mile from the town of Pescadero extended north and south 
for about 50 feet, and a farm house a mile farther down the road was nearly shaken off 
its foundations. Dishes fell from the shelves in this house, and water oozed out of level 
ground near by. 

(G. A. Waring.)— On Butano Creek there were slight cracks in the road, and the streams 
were muddy. People said the shock was felt very distinctly, and dishes generally fell. 
The houses were all light, low buildings, and were not damaged. At a sawmill a mile 
east up this creek, there was no damage; and altho the banks beside the road showed 
traces of caving, there were only slight cracks, the longest one being in the middle of 
the road above the creek, running N. 67° E. for a distance of about 50 feet. 

Along the main road from Butano Creek to Little Butano Creek, then across by trail 
to Pigeon Point, the same effects were noticed. Near a house on the level creek bed 
of Little Butano Creek, 4 cracks averaging 3 inches in width and about 20 feet in length 
ran N. 33° EK. The only crack noticed along the trail toward the coast was 1 mile north- 
west of the place where Little Butano Creek turns from southwest to northwest, and 
was about the same length, but ran N. 3° W. 

Pomponio Creek road (F. Lane). —On the Pomponio Creek road, chimneys were 
shaken but not destroyed. A big slide above the last house forced the observer to leave 
the road and take the trail, which rejoins the road a half mile farther on. 

Four miles from the town of Pescadero, on the east side of a bridge over Pescadero 
Creek, the ground had sunk 2 inches and the aperture filled by the land sliding. 
A mile nearer the town, the road had dropt 5 feet, but had been filled by a big slide. A 
house at this point was quite intact, but the chicken-house near it was carried down and 
partly buried by the landslide. On Eues Creek, near its junction with Pescadero Creek, 
a hillside had started to slide and apparently needed only to become rain-soaked to con- 
tinue the slipping. Wherever there were buildings in this region, no damage had been 
done except to chimneys, which had fallen. 

The Coast from Pigeon Point to Ano Nuevo Bay (H. W. Bell). — At Pigeon Point the 
brick light-house, 125 feet high, showed a slight crack all the way around inside, about 
40 feet from the ground. This crack did not look.dangerous. Another crack 20 feet 
higher up dated from December 17, 1904, the keeper explained. The base of the pedestal 
holding the lens was slightly cracked, but the lens was intact. In the houses near the 
light-house the damage was slight; brick chimneys had not fallen, tho slightly cracked, 
and the same was true of plastering. A mile west of the light-house a few slight cracks, 
with a direction of N. 28° W., were observed. 

Leaving the coast road at the fork halfway between Pigeon Point and Franklin Point, 
and going northeast along Gazos Creek, then southerly to the crossing of Whitehouse 
Creek, then back again to the ocean road near Franklin Point, few traces of the shock were 
noticeable. A small landslip, 0.25 mile up the east side of the short creek which flows 
into Gazos, just west of the fork of the road which continues northwestward to Little 
Butano Creek, showed a 2-foot vertical displacement at the top, and the land had shoved 
into the road below. This slide measured 150 feet from its top to the road, and its width 
at the road was 100 feet. 

Along this route from Gazos to Whitehouse Creek, 0.125 mile from Whitehouse Creek, 
at several farm houses brick chimneys were down, houses slightly moved on their foun- 
dations, dishes broken, and plastering cracked. A half mile northeast of the mouth of 
Whitehouse Creek the same kind of disturbance was found. The intensity was apparently 
uniform with that at Pescadero. At the Cascade ranch, 0.25 mile northwest of Green- 
oaks Creek, the shock was even stronger than on Whitehouse Creek. Cows were thrown 
off their feet, chimneys were down, the house cracked, and nearly all plastering fell off. 

T 


274 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


(H. W. Bell.) —It was reported here that along the Ocean Shore construction work near 
Bolsa Point, a concrete pipe 24 inches in diameter and 6 inches thick, embedded in clay, 
had been cracked by the shock. The keeper of the Ano Nuevo light-house says a distinct 
rumbling preceded the shock, which came at first rather gently, followed by a hard, con- 
fusing shake. A brick chimney in the house near by was cracked and twisted 0.75 inch 
out of place, but the new tile and concrete building was unhurt. The ocean became no 
rougher, but had a peculiar greenish hue for several days after the shock. At Pigeon 
Point the shock was less severe, and little damage was done to the buildings, altho 
cracks in the light-house, caused by a former quake, were opened somewhat wider. 

Following the road from the Cascade Ranch across toward Ano Nuevo Bay, the in- 
tensity seems to have decreased. At a house 0.75 mile southeast of where the coast road 
crosses Greenoaks Creek, a few dishes fell; plastering was but slightly cracked, and a 
water-tank stood. Half a mile north of the mouth of Ano Nuevo Creek, the brick chim- 
ney was knocked from a house, plaster was cracked, and cattle were caused to stagger. 
Half a mile southeast of where the main road crosses Finney Creek, a ledge of shale had 
been knocked into the gulch. The largest piece which fell had an unbroken surface of 
about 4 square feet. The almost horizontal edges of shale beds near a house at this point 
were knocked down. <A long, narrow landslide above a house 0.75 mile northeast of the 
mouth of Waddell Creek had landed against the end of the house, taking out a strip of 
earth below a spring and causing a good supply of water to issue forth. This slide 
appeared to be partly due to the large amount of water present. At the house the chim- 
ney was cracked, but dishes did not fall from their places. 

Turning north by a trail opposite Greyhound Rock, evidences of about the same inten- 
sity were found. Dead trees had fallen here and there, but in no uniform direction. 


LOS GATOS TO SAN JUAN. 


Los Gatos, Santa Clara County (I. H. Snyder). — Los Gatos, population 1,900, is partly 
on a mountain slope and foot-hills, and partly on river deposit. It is surrounded by 
hills on three sides. Los Gatos Creek runs thru the center of the town from south to 
north. The earthquake shock was violent, but apparently not so severe as in the central 
portion of the valley. Nearly all business houses were damaged, and about one-third 
of the plate glass fronts were broken. Much plaster fell both in Los Gatos and in the 
surrounding country. Chimneys fell in many different directions, and nearly half of the 
damaged chimneys left standing were twisted. About 80 per cent of all the‘chimneys 
were destroyed or damaged. Brick fronts were nearly all cracked, and one fell out. 
There were about a dozen upheavals of sidewalks, mostly on north and south streets. 
Grocers and druggists lost quite heavily in breakable goods. 

The direction of the shock seemed to be in general north and south, altho there were 
certainly severe vibrations from nearly all points of the compass, while some persons are 
certain that there was a vertical motion, especially near the beginning. After the shock 
was over, our chandelier was still swinging violently north and south; a near neighbor’s 
lamp swung in the same way; another hanging lamp 0.5 mile west swung northeast and 
southwest. East and west shelving in stores suffered rather the most, tho a store in 
Kast Los Gatos, with shelves north and south, suffered fully as much as any. 

Of the 3 pianos seen in Los Gatos that were moved, 2 went to the south about 3 feet 
and one moved east the same distance. A small seismograph made several years ago 
was in working order, but there was no record, the needle having been thrown off by the 
extreme movement. 

Mr. Lund, of Los Gatos, was one of the few people outside when the shock came. 
He is positive the premonitory roar came from the south and traveled to the north. 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 275 


Mr. Dan Pickering, living about a mile south of Santa Clara, on the Santa Clara and Los 
Gatos road, was standing outside his barn when he heard the sound, which he compares 
to a stampede of cattle coming from the southeast. His tank and wind-mill fell diagonally 
actoss the foundation to the northwest, after swaying heavily three times; first to the 
northwest, then to the southeast, and finally to the northwest. He states that the 
ground rose and fell in waves a foot high. Others report that the orchards seemed to 
be agitated by a wave-like motion. 

On the ranch of Dr. Tevis, about a mile from Alma Station, where the land is rolling 
and wooded, the ground was fissured and the bottom of an artificial lake was upheaved. 
(Plate 139c, p.) The cracks and fissures, of which there are many, run mostly north and 
south, and vary in length up to 100 feet, and in width from 0.5 inch or less to 20 inches. 
While a good many of the openings were parallel to the slopes and were caused by the 
ground starting to slide, others crost the roads and could be traced some distance up 
the banks. A board fence was splintered where it crost a fissure. The upheaval of the 
lake was caused by a closing together of the sides, shown by the heaving up of parts of 
the retaining dam at the lower end of the lake. The rise of the bottom is roughly 10 feet. 

Three of the large cemeteries of the Santa Clara Valley were visited. In the Los Gatos 
Cemetery, on the New Almaden road, no monuments were thrown. In the Protestant 
Cemetery, 0.75 mile southwest of Santa Clara, 31 monuments were thrown down and 
mostly broken. Of these 10 fell to the south. In the Catholic Cemetery, 0.25 mile nearer 
Santa Clara, 26 monuments fell, of which 10 fell to the south. The direction of the fall 
of monuments in these two cemeteries is here tabulated: 











N NE E SE. S SW. 
Protestant . . 3 7} 1 10 1 
Catholic. . . 5 1 6 2 10 1 








* Of these, 4 fell from pedestals which leaned to the east. 


In the Catholic Cemetery three monuments were turned on their bases, two clockwise 
and one counter-clockwise. 

The Santa Clara city water-tower, with large tanks on top, fell to the southwest. 

(F. H. McCullogh.) —I was in bed in Los Gatos and was awakened by the shock, which 
seemed to be a violent but irregular shaking back and forth in a northeast-southwest 
direction, altho objects were overturned in an easterly or southeasterly direction. A 
double bed on a polished floor rolled 4 feet from its position. One heavy marble clock 
was thrown off its shelf. Ornaments and bric-d-brac were thrown down. Two tables 
were turned upside down. Plastering was cracked. Chimneys were cracked above roof, 
but not thrown. In the town I could hear of only one chimney which was uninjured; 
90 per cent of all chimneys were thrown down. Water in a reservoir 30 feet in diameter 
and 10 feet deep was thrown out so as to lower the level of the water nearly 2 feet. 

Lexington (H. R. Johnson). — At the Lexington saloon, 3 miles south of Los Gatos, 
very little damage was done. 

At the Averill place, 1.5 miles west of Wright’s Station, a water-tank was moved a foot 
toward the south. A piece of board several feet long, which was leaning against the 
tank-house before the shock, was said to have been found wedged between the bottom 
of the tank-house and the foundation. This would necessitate a lifting of the tank-house 
in a vertical direction on that side, which might have been accomplished by the tank- 
house rocking from side to side. 

Summit Hotel (H. R. Johnson). — At Summit, a summer resort, the new hotel and 
several small cottages were all thrown toward the north. The main fault fracture is 


276 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


about 500 feet northeast of the hotel, and a secondary crack close to it had a downthrow 
of from 5 to 7 feet on the north or downhill side. The crack was about 4 feet wide here, 
and the line of fracture was parallel with the direction of the ridge. ‘The Summit school- 
house was dropt 4 feet downhill from its original position toward the northeast. In the 
vicinity of Summit several redwood trees were snapt off. 

Just north of Wright’s Station, on the west bank of Los Gatos Creek, there was a land- 
slide 0.5 mile wide which had slid into the creek and dammed it. ‘The top of this slide 
was near the Summit school-house and was close to the main fault-line. The Hotel de 
Redwood was destroyed by the shock. 

Wright Station (Miss F. C. Beecher). — Miss Beecher’s home is on Loma Prieta Avenue, 
on the county line, 1.5 miles in an air-line from Wright’s Station. The house stands on a 
ridge at an elevation of 1,700 feet. There were 2 maxima in the shock, of about equal 
intensity. The movement in the first was from south-southwest to north-northeast. 
All light objects were thrown down. Furniture against south walls was thrown down 
or moved out; objects against other walls were not moved as much. A small square 
piano which stood a few inches from a northeast wall ran back against the wall to the 
north with sufficient violence to break a knob off one leg. It then moved back to its 
original position, then 5 inches west. Then the two legs to the north jumped 6 inches 
south. These movements were determined by the marks upon the floor. A wash-basin, 
and a pitcher full of water, in an upstairs room, were thrown south, and the basin was 
found with the pitcher standing in it, uninjured but empty. A table in the middle of 
the same room fell to the north. A piano in a neighboring house, a heavy upright, was 
moved across the room to the northeast. 

All brick chimneys on the ridge fell, mostly to the north. Trees at the foot of the ridge 
were bent over to the north-northeast. Half a mile to the northwest of the house, a 
fissure 2 feet wide appeared, from which bad-smelling gas emanated. The fissure runs 
from north to south, and the earth was piled up on the west side from 2 to 4 feet high 
across the road. On Highland, a mile to the west, a fissure 5 feet wide was opened at an 
altitude of 2,500 feet. A building standing close to a fissure was entirely uninjured, while 
others a little farther off were wrecked and one collapsed. Most good buildings in a belt 
0.5 mile west of the house were wrecked, while barns and shaky buildings stood. About 
1.5 miles west, a house split open. Gulches appear to have been contracted, as the bridges 
crossing them show that they were squeezed. The banks of Burrell Creek appear to have 
approached each other, so that the creek has become very much narrowed. Water-pipes 
were broken and twisted, and filled with dirt. Water was thrown out of tanks, but the 
tanks were not overthrown. ; 

During the shock the waves appeared to oscillate in a north and south direction at 
first. There were at least 26 shocks during the first 26 hours after the main shock. 

Burrell School (H. R. Johnson). — Near the Burrell school-house, 1.5 miles southeast 
of Wright Station, a crack extends across the road by a blacksmith shop and shows a 
downthrow of 4 feet on the northeast. The blacksmith said there was a strong odor of 
sulfur for 5 or 10 minutes after the shock. A well near by has had sulfur in the water for 
a number of years. 

Morrell Ranch (H. R. Johnson).—The Morrell ranch is located 1 mile south of Wright’s 
Station and is on the line of the fault. The house itself was built exactly upon a fissure, 
which opened up under the house at the time of the earthquake. ‘The house was com- 
pletely wrecked, being torn in two pieces and thrown from its foundation. (Plate 107B.) 
There was an apparent downthrow upon the northeast side of the fault, as seen in the 
orchard; but under the house the vertical movement was not so apparent. An espe- 
cially strongly constructed wine cellar built into the side hill had the upper portion thrown 
3 feet northeast, directly away from the fault-line. After the shock this upper portion 


PLATE 107 








A. Shortening of railroad track between Los Gatos and Santa Cruz. G, A. W. 





B. The Morrell house, near Wright Station. G. A. W. 



















wr er \ oe an i? 
: re. a 
: 
4 
‘ o 
a na 
- 
x 
‘ 
. g ooh) aay a aw ie teeeraas 
: Se tod og ee has 
- hy i= nt ae ae -) 
. . 
s : o ‘ 
Bm . ¥ ‘ 
F « 
Lr rom 
— a 
. * 4 gx 
t Nos vy 
. A . 
, Fi 
a 
, F ee ia 
A 
i 4 
d - Ss - . 
, 
c’ Ls ¢ 
f i 
i= 
n 
P P ym 
r aes é 
i 
‘ 
“ , 
; = 
3 
' 
*- ‘ 
: 
n > 4s ys 7 
' 
iJ 
HVT RR) ' 
' 
‘ 
° 
; 
i 
’ 
on. 
% 
ry 
rie’ Ms 
. i j , ae 
A ; 
: ; . 
=F 
- ; 
* P 7 
Say > 
t ire 
fi . o Y. + 
Pn 
; F 
“ 
wt \ 
' Y al “g 
# » 
‘a + ‘ 
a oe wat: 
- , ~~ a 
' 5 A 
d 
’ . cee 1 ry 
‘ a - * ‘ ae 
i i ' . ‘ - gilt? « * . 
. eo bh es SR 7 ay 
2 : a ; Vee 4 ve = " ; 
om hee a ae hewn Bem Sate? stents FSD Sep ee Seem i aes ot tn . oe 
4 ” a ey a Sis 0 eat el! EA) Ae . 
‘ y am : a ¥. Bre ¥ ee ae ee 
Tv et eee SA oe Le 
5 i -m . 5 ",* : ea 
; , Pi’ ’ - * ihe 
yesh Ry en yy role Oe ce ara 
ard : - -" 
é ¥ 
Fe hh 
¥ < > 
' ‘ 
, ‘ & 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 277. 


of the house was left resting upon the wine tuns, and not upon its original upright sup- 
ports (fig. 56). The fence and road near the house were crost by the fault and showed an 
offset which indicated a relative movement of the southwest side toward the southeast 
(plate 648). One fence was broken apart, but the other was merely bowed, due probably 
to the resistance and drag of soil occasioned by a well-packed roadbed. The fruit-tree 
rows which crost the fault-line at approximate right angles were put out of alinement. 




































































aa 





SIF S —- A, 
7, NYT / 
= LY ff) 
; fj : 
| Vas, 
' = ile = , | fy 4 
tT / 
a is 
72 prs Bee 
I ae te 


Fira. 56.— Section thru winery at Morrell ranch before and after the shock. 














A feature associated with the movement of soil along the fault-line is shown in the 
accompanying sketch, fig. 57. The “splintering” of the main fracture raised a long, low 
ridge across which a creek had been forced to cut its way thru a vertical distance of 1.5 
feet to get down to its original level. 

Between Wright’s and Alma the railway track was buckled. (See plate 107A.) 

(D. S. Jordan.) —At Morrell’s ranch, about 4 miles above Wright’s, a large 2-story 
house with a wing stood on the slope of a hill. The east side of the house was much 
higher above the ground than the 
west, and stood on wooden piers about 
7 feet high. The earthquake crack 
past thru this ranch, a branch of it 
going under the house. The main 
body of the house was thrown to the 
east, away from the crack, the ground 
there slumping several feet and the 
house being almost totally wrecked. 
All thru the orchard the rows of trees 
are shifted about 6 feet, those on the 
east side being farther north, and the 
east side, which is downhill, seems to 
have fallen. The crack is largely open 
and in one place is filled with water. 
This should be attributed to slumping. 
A little farther on, the crack passes 
thru a grassy hill on which there is no 
slumping. The Morrells say that this » 
hill has been raised. What appears to 
be the fact is that the east side of the 
hill overrides the other. The whole top of the hill is more or less cracked for a width of 
about 10 feet. The east side is a little higher than the west side, and it looks as tho the 
hill had been shoved together and raised, the east side overriding. About 1 mile beyond 
Morrell’s house, at the end of the ranch, there is a blacksmith shop, and the road is crost 
by the crack. Here there is a break of 3 or 4 feet like a waterfall, the east side being 
the lower; but this is part, I take it, of the general slumping of the east side of the crack 







4 
Morrell house 






Scale in feet 


10) 150 ae 






Fic. 57. — Displacement on auxiliary crack, Morrell ranch. 
p ; 


278 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


where it stands near the ravine above Wright. Morrell’s place is right over the Wright 
tunnel, the tunnel and the rocks near by being of finely broken rock and very much subject 
to slides and other breaks. At Freely’s place, 4 or 5 miles north of Morrell’s, some 15 
acres of woodland have slid into Los Gatos Creek, making a large pond. There are many 
other slides in the neighborhood and many broken trees. Farther on, the crack goes into 
Hinkley’s Gulch, in which the Loma Prieta Mills are situated, and which are buried under 
the slides. The slides which obliterated Fern Gulch at Skyland do not seem to have come 
from the crack, but seem to lie to the west of the crack. 

About four miles south of Wright Station (Mr. L. E. Davidson). —I was camping in the 
Santa Cruz Mountains. My attention was first arrested by a slight rumbling noise; then 
the house trembled for 4 or 5 seconds, and this was followed by a heavy rolling motion 
almost east and west. A heavy trembling came again for several seconds, then the heavy 
shock that threw down the chimneys. Tables and even chairs were upset. This must 
have lasted about 4 seconds; it then gradually died away. The whole time must have 
been all of half a minute. During the day several slight shocks were felt; about 2" 
and 2" 30" p.m., two rather heavy shocks came. 

The ridge on which we camped was full of cracks, ranging up to 2 and 8 feet in width, 
and in length from a few rods to 0.25 mile, all trending west of north to northwest. 
All chimneys on this ridge were thrown down; several houses were completely wrecked ; 
branches were broken from the trees, while many of the trees broke in two and others 
were uprooted. The canyon south of us was filled with landslides. In this canyon the 
stratification of the rocks is plainly shown. The strike is northwest-southeast and the 
dip is almost vertical. The cracks coincide in direction with the strike of the strata. 
Cold water was flowing from some of the cracks. I obtained a small bottle of crude 
oil from Mr. Sutton, which he said was dipt up from the ground on his neighbor’s 
ranch, several hundred gallons of oil having run out of the ground since the earthquake, 
where there had been no sign of oil before. 

Skyland, Santa Cruz County (T. Wightman). — Mr. Wightman’s bed traveled across 
the room to the south, and he was under the impression that the house was falling to the 
south. Some houses in the neighborhood fell completely, and some collapsed on their 
foundations. The two chimneys of his house were thrown, one coming through the 
roof. Some pictures hanging on east walls were turned withstheir faces to the wall. 
Large landslides occurred in the neighborhood. 

Soquel, Santa Cruz County (Miss M. E. Baker). — The house is on the first high 
bench above the stream in Soquel Valley, with high hills té the north and the east. 
At the first movement of the earthquake, chimneys were thrown to the South; at the 
second, mantel ornaments, books in the library, fruit jars in the pantry, etc., were thrown 
toward the north. Some houses in the vicinity had chimneys and objects partly turned 
around. There were two maxima in the shock, the first being the stronger, and the 
direction of movement was from north to south. In the second part of the shock the 
movement seemed to be a twisting one. 

Chittenden (G. A. Waring). — At Chittenden Station evidence of a most violent dis- 
turbance was found. The cottage of the foreman was moved 5 inches westward; an 
upright piano was thrown northwestward upon its back, and electric drop-lights swung 
so as to break against the ceiling. A large frame dairy building on underpinning was 
moved 3 feet northward, as was a smaller building. The oil in a large tank was 
thrown southeastward, badly bending the tank and smashing the protecting shed. 
' (See fig. 58.) The railroad office was not moved from its foundations, but the porch 
roof was jerked nearly off and a 1,000-pound safe was thrown southeastward upon its 
back. Three freight cars on the side-track, loaded with beans, were tipt over to the 
northeastward. At the time of the shock a north-bound freight train was running at 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 279 


about 30 miles an hour, a short distance south of the bridge over the Pajaro. About 
10 cars in the middle of the train were thrown off on both sides of the track. The 
track at the southern end of the Pajaro bridge sank from 2 to 4 feet for a distance of 
150 yards, and between Chittenden and the bridge the track was bent in an S-shaped 
curve in several places. The concrete piers of the bridge were cracked, and the granite 
cappings shifted as before noticed. (See plate 658 and fig. 43.) There is much sulfur, 
oil, gas, and water in the hills here. A marked increase was noted in the flow of oil 
and water, and more gas and sulfur became associated with them. It is said that since 
the earthquake 16 years ago small shocks have been felt each spring, often severe enough 
to crack chimneys, and a deep well becomes muddy 2 or 3 days before these occur. 


Housed Qil-tank 


oA 
- 


Office Shed,on 12", \ 
me underpinning J} Sft. 


Waiting shed 
eae 


Pp. 





Fie. 58.— Displacement of buildings at Chittenden. 


Fifty-two distinct shocks were felt during the day of April 18, and 32 that night. 
From 1 to 4 shocks were felt every day thereafter up to May 16, and from 2 to 5 
occurred every night. Two miles north of San Juan, Mr. Canfield’s house, at the foot 
of the hills 0.5 mile east of the fault, was moved bodily 2 inches westward, and the 
chimneys were completely thrown down; but a house 150 yards west of the fault, altho 
considerably shaken, appears to show the shock to have been less severe on that. side. 

San Juan (G. A. Waring). — The town largely escaped by virtue of being on solid 
ground. A large inner wall at the San Juan Mission fell, but it was no doubt weak, as 
other parts of the building appear unhurt. Only one or two chimneys in this village 
fell, but in the bottom-land between San Juan and Hollister the condition of the houses 
indicates a heavier shock on the low ground. 


SANTA CLARA VALLEY. 


Information regarding the distribution of intensity in Santa Clara Valley has been 
contributed by a number of observers whose names are given with the paragraphs deal- 
ing with the respective localities reported upon by them. 

Newark (¥. EK. Matthes).— Nearly all brick and tile chimneys in the village were 
broken off; the direction of throw varied. Plaster cracked and fell in quantities on 
the lower floors of hotels and several other buildings. There are no brick houses in the 
town; and most of the frame dwellings showed no effects of the shock, At the depot the 


280 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


water-tank fell, the supporting trestle being practically demolished. The track suffered 
a slight shifting in several places north of the village. Cracks opened in the ground in 
the vicinity of 2 small watercourses, but on a less extensive scale than that noted at 
Alvarado. Some of them crost the railroad track. In every case they emitted the 
same bluish sand (with the water) that had been found near the Alameda Sugar Mill. 
In one place, 1.5 miles northeast of the village, considerable water was still left standing 
in shallow ponds. According to neighboring ranchmen, these ponds had not existed 
prior to the earthquake. 

Centerville (F. IX. Matthes).—The amount of destruction here seems greater than in 
the neighboring towns, but this is in large measure due to the presence of a number of 
poorly constructed brick houses. All of these had suffered severely, the walls being in 
part thrown down. The bank building was more seriously damaged than most build- 
ings, the walls being partly demolished and the roof having caved in. With very few 
exceptions all the brick and tile chimneys were broken off. Window panes broke in 
several stores. No cracks in the ground were found or reported. The direction of the 
shock was not agreed upon by the residents; according to some it was north-south, 
according to others east-west. 

Mission San Jose (S. Ehrman). — Nearly all chimneys were thrown down, and plaster 
in houses cracked; the direction of the throw of chimneys and objects being chiefly 
from north to south. Some objects were rotated clockwise, and hanging objects were 
caused to swing. | 

Irvington (F'. E. Matthes).— Destruction similar in degree to that at Centerville. 
Every brick house was more or less extensively damaged; portions of walls fell in some 
instances, and cracks in brickwork were common to all. The large brick and stone 
buildings of the Palmdale Winery suffered more severely than any, and large portions 
of them will have to be rebuilt entirely. Only a few chimneys were left standing in the 
village. Plaster cracked and fell in large flakes in several houses. ‘The upper stories 
apparently suffered less than the lower floors. 

Milpitas (F. E. Matthes). — Nearly all chimneys were here thrown down, a few, 
including a very short one on the depot, being left intact. There are no brick buildings 
in the village and the destruction seems insignificant. The hotel slipt on its founda- 
tions, but was almost repaired at the time of the visit. A small adobe house in the 
southern part of the village was fairly demolished; it was known to be an old and weak 
structure. A water-tank and wind-mill were thrown down, support and all, about a mile 
south of town. They fell to the south. Another tank, north of town, appears to have 
fallen to the west. Several other tanks in this neighborhood were found intact. Of 
the two bridges over Coyote Creek, the northern one suffered some damage by displace- 
ment of end supports. It was unsafe to travel over at the time of the visit. The south- 
ern bridge was found intact, the end supports showing signs of but small movement. 

Agnews (F. E. Matthes).—The insane asylum, consisting of three tall and three minor 
brick buildings and some small frame structures, suffered very severely. Every one of 
the brick structures was damaged beyond repair and will have to be entirely rebuilt. 
The main buildings were long, 3-story brick structures oriented north and south, 


with large projecting bay windows at their north and south ends. These were destroyed, 


so that both buildings are open at their ends. The fall of these walls caused the caving 
in of the roof, and the sagging down in some places of the floors. Numerous lives were 
lost; in all 112 dead being found in the ruins. The administration building was partly 
wrecked by the fall of its tower, which crashed thru the roof and all the floors, carrying 
with it a number of people. In nearly all cases the north and south facing walls were 
thrown out, while the cast and west facing walls were, as a rule, better preserved. The 
shock seems to have been north-south principally, judging from these data. 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 281 


The tall brick chimney of the engine house (100 feet high) broke off 20 feet above the 
ground and fell in a northeasterly direction, without touching any other structure. 
Frequently window-panes remained unbroken in the lower parts of walls whose upper 
parts had been completely demolished. (See plate 108a, B.) 

The extent of the destruction is in some measure due to the use of weak mortar, the 
bricks having, as a rule, fallen separately rather than in aggregates. It is believed that 
well-built buildings would not have suffered such wholesale destruction as was witnessed 
here. 

Alviso to Milpitas (G. F. Zoffman). — Evidences of the earthquake at Alviso are 
shown only by fallen chimneys and cornices and by cracked walls of the brick ware- 
houses. No buildings were demolished and little serious damage of any kind was to be 
noted. From 1,500 to 2,000 feet west of the bridge over Coyote Creek, cracks cross the 
road in front of the Boot ranch-house, and several of them occur in the road leading to 
that house. (Plate 1408.) Some of these cracks are about 6 inches wide and have 
a general bearing of N. 43° W. Immediately after the earthquake, water flowed from 
some of them and brought up sand, which was heapt up about 6 inches high. The water 
ceased to flow after the second day. 

Near the dwelling house on the Boot place, the ground settled 11 inches on the east 
side of the crack. The fissures past under the corner of the dwelling house and the 
building was partly thrown from its foundation. The cellar beneath it was filled with 
water to a depth of from 2 to 3 feet. There is a capped artesian well in the yard of this 
house, and about this well is a pool of water 12 feet across. The west side of the pool 
was lifted 1 foot higher than the east side, and fish were thrown out of the pool. A 
hundred feet east the fissures past under the barn, and the ground settled on the west side. 
Water flowed from cracks in the yard and piled up sand 6 inches high on both sides. 

People living near Coyote Creek state that the water rose between 2 and 3 feet im- 
mediately after the earthquake; and up to April 26 the water in this stream had not 
returned to its normal level. At the bridge over Coyote Creek, on the Alviso-Milpitas 
road, the concrete abutments were thrust inward toward each other about 3 feet. A 
pile driven in the middle of the stream, which had been cut off below the water-level, 
was lifted about 2 feet and now rises above the water. 

About 150 feet north of this bridge the banks of the stream cracked, the fissures 
running parallel with the channel and the land on the creek side sliding toward the 
stream. (Plate 1404.) West of the stream, in an adjoining field, water rising thru 
cracks built up many craterlets of sand. (Plate 1434.) Residents of the vicinity state 
that the water rose 3 or 4 inches above the tops of these craterlets while they were 
being formed, and that it ceased to flow toward the end of the second day after the 
earthquake. 

In the road running northward along the west side of Coyote Creek from the bridge, 
many large cracks opened. Five hundred feet north of the bridge the cracks were 2.5 
feet wide and 3 feet deep when the place was visited April 26. Farther north the cracks 
were very abundant, mostly parallel with the road, and some were 4 feet deep and 3 feet 
wide. A quarter of a mile north of the bridge, the whole road was shoved eastward into 
the channel of the creek, and with it a large number of willows and cottonwood trees 
that grew along the banks. Just south of this place the road was broken up badly for 
a distance of 300 feet. One of the largest cracks in the road was 5 feet wide, 6 feet 
deep, and more than 100 feet in length. The bearing of the fissures at this place was 
N. 28° W. For the most part the principal features were approximately parallel with 
Coyote Creek. 

At Mrs. North Whitcomb’s ranch, on the south side of the Alviso-Milpitas road, be- 
tween Coyote Creek and Milpitas, the prune orchard was cracked and the ground shifted 


282 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


at several places. The ranch-house, of concrete with a wooden upper story, was cracked 
across the northwest corner and settled slightly on the northwest side. In the back 
yard were fissures 1 foot wide, running about N. 13° W., with a downthrow of 1 foot on 
the east side. Some of the prune trees in the orchard are 2 feet out of alinement, and 
some as much as 6 feet. The lateral displacement here shows a relative movement of 
the south side toward the east. Considerable sand was brought up by water flowing 
from the cracks in this orchard. 

In the town of Milpitas all the chimneys were thrown down, as well as 3 frame build- 
ings. The hotel fell from its underpinning and sank bodily about 3 feet. The streets 
near it were not disturbed. 

Warm Springs (G. F. Zoffman). — The Warm Springs Hotel, a large 2-story build- 
ing, was but slightly damaged, only a little plaster falling. No buildings were damaged, 
beyond the falling of two chimneys. 

Milpitas-San Jose Road (G. F. Zoffman).— About 0.5 mile south of Milpitas, on the 
Milpitas-San Jose road, cracks were formed across the road. They did not, however, 
appear to have any definite direction, and were so small that no lateral movement was 
discernible. At the County Alms House, about 1 mile south of Milpitas, two chimneys 
were thrown down and considerable plaster fell. On the north side of the bridge which 
crosses Coyote River, on the San Jose-Milpitas road, some cracks were found but they 
were evidently caused by the sliding of the banks. The bridge was not damaged. 

The damage in the section of country lying between Milpitas and San Jose was nearly 
uniform. About 90 per cent of the chimneys were thrown down and in all houses that 
were plastered considerable plaster fell. Articles in the houses were thrown over, and 
much water and milk was spilt, altho it does not appear to have been in any partic- 
ular direction. Cracks like those which were observed in the ground on the Milpitas- 
Alviso road reappeared on both sides of the Coyote River at intervals all the way to 
San Jose. Altho they occur in a general north-south direction, it seems probable that 
their origin was due to the unstable condition of the alluvial deposits which underlie 
the valley. 

Alum Rock Road (G. F. Zoffman). — Starting from San Jose and going toward Alum 
Rock, it was observed that the shock had decreased from an intensity of 1X at San Jose 
to an intensity of VI at Alum Rock. No cracks were found between Coyote Creek and 
the mountains, but in the valley at least 90 per cent of the chimneys were thrown. At 
the mouth of the Alum Rock canyon, a count of the fallen chimneys revealed the fact 
that the percentage had dropt to 50. At Alum Rock no chimneys were damaged nor 
had any movable objects been overturned, altho the water in sulfur baths had splasht 
up about a foot on both sides. 

Calaveras Valley to Evergreen and vicinity (G. F. Zoffman). — Going from Milpitas 
toward the Calaveras Valley, chimneys were all thrown down on the flat lands between 
the village and the foot of the grade leading over the ridge to Calaveras Valley. 

In Calaveras Valley all the brick chimneys were thrown down, tho there were only 
a few in this valley. No damage to houses is reported. Mr. Hadsell, in charge of the 
property of the Spring Valley Water Company, which has begun to construct a dam 
at the north end of the valley, states that there was no shifting of the strata im the tun- 
nels, and that no damage had been done the property. 

Between this place and the head of Alum Rock Canyon, the residents stated that 
cracks appeared across the road in several places; but altho this was in the proximity 
of the Calaveras Valley fault-line, which passes thru this region, it was not possible to 
verify their statements. Mr. Robert Ingleson, who lives in section 22, on the ridge 
east of Calaveras Valley, reports that the shock was not severe there. A long slender 
bottle standing on a table in his house fell over, but a lamp on the table was not upset. 


PLATE 108 





C. Phelan Building, San Jose, 





B. Agnew’s Insane Asylum, North side. F. EB. M, D. Hall of Records, San Jose, 





PLATE 109 





A. High-school, San Jose. 





B, Hotel Vendome, Annex, San Jose, 





b> 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 283 


Water in a horse-trough spilt out, and the trees waved as if there had been a wind. 
The earthquake consisted of two separate shocks, accompanied by a roaring sound that 
seemed to come from the north. Springs near his house became muddy after the shock 
and remained so for 2 or 3 days. The flow of the springs increased to about four times 
the usual amount. 

Along the road down Penetencia Creek, a considerable amount of débris had slid into 
the road, in many places obstructing all travel except for pedestrians; but no evidence 
of cracks could be found. 

In the region between Alum Rock and Evergreen, about 50 per cent of the chimneys 
were thrown down, but none of the buildings were materially damaged. 

As the Santa Clara Valley was once more approached, the intensity of the shock per- 
ceptibly increased. At Evergreen, about 1.5 miles from the foot-hills, considerable dam- 
age was done; all the chimneys, all the road tanks, and nearly all of the wind-mills in 
the neighborhood fell. None of the houses were demolished, but some were shifted on 
their foundations. 

(H. R. Johnson.) —The Pierce ranch-house, 3 miles southeast of Evergreen, was 
badly shaken; plaster and chimneys were down and much chinaware was broken. This 
house is on the gravel of the large alluvial cones which have been built out along the 
southwest face of the Monument Peak Range, where the stream debouches upon 
the plain. A water-tank fell northeast and southwest where the Tully road crosses 
the Coyote River 1.5 miles northeast of Oak Hill Cemetery. 

At the Mayne ranch, 3 miles south of Oak Hill Cemetery, where the New Almaden 
Railroad crosses the Downer road, water from tanks and troughs was spilt in a north- 
west and southeast direction. To the west of the Mayne ranch, at the Downer ranch, 
a water-tank fell to the west. Mr. Downer said that milk in pans was spilt in the 
same direction. 

At the Poncelet ranch-house, on Llagas Creek, 7 miles southwest of Madrone Station, 
only one chimney fell and no dishes were broken and no, clocks stopt. This place is 
only 3.5 miles northeast of the fault-line and is situated directly upon rocks of the Fran- 
ciscan series. 

The Saunders ranch is 3.5 miles southwest of Madrone, on the Madrone road. The 
shock was quite heavy at this place; the chimneys were thrown down, dishes broken, 
and portions of what appeared to be quite solid and massive rock outcrops were thrown 
from the steep hills near the house. South of the Saunders place, 1.5 miles, a water- 
tank was thrown down. 

Santa Clara (G. F. Zoffman).—Nearly all the brick chimneys were thrown down and 
most of the brick buildings were damaged. At Santa Clara College the rotary motion 
of objects was shown by the turning of statues in the chapel thru an angle of 130°. In 
the library of the same institution four marble statues, with square bases, fell in three 
different directions; one facing 8. 87° W., another, facing N. 87° E., fell toward each 
other, while the others, facing, respectively, N. 3° W., S. 3° E., fell N.3°W. Professor 
Ricard, of the Science Department of the College, states that the vertical movement threw 
a wind-gage out of a socket a foot deep. This was the only evidence at the College 
of vertical motion. | 

Cemeteries (G. F. Zoffman). — A count was made of the number of tombstones thrown 
down in the Santa Clara Cemetery and the various directions in which they fell were 
noted. From these observations it seems that the shock was slightly more intense 
toward the easterly direction than toward the westerly. Twenty-five headstones were 
down and their respective directions of falling were, 3 N. 17° E.; 1 N. 32° E.; 1 N. 37° E.; 
On ee Ni tee yn 1S, 06 Hes 6S, 28° His°38 8.239 B.3.1 8. 3° E, ; 
ool Wal, eanie eo bivecs W,, tN. %3° W,; and 1 N. 13° W. 


284 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


At Oak Hill Cemetery the larger percentage of tombstones fell in an easterly direction. 
Out of 34 monuments overthrown, 21 fell toward the east or nearly so; 6 toward the 
west or nearly so; and 1 toward the north or nearly so; 3 fell northeast, one fell north- 
west, 1 fell southeast, and 1 fell southwest. Out of 6 round monuments that were noted, 
4 fell toward the east, 1 northwest, and 1 north. Since these could fall in one direction 
as quickly as another, it is evident that the greatest movement of the quake must have 
been toward the east at this particular place. 

At the Catholic Cemetery, about halfway between San Jose and Alum Rock, only a 
few monuments were overturned; they fell as follows: 2 north, 3 south, 1 northwest, 2 
east, 1 west, 1 southeast. 

San Jose (G. F. Zoffman).— The earthquake threw down many brick and stone 
buildings (plates 108c, p, 109a, 1108, 111, 112, 113), and with the exception of 4 or 5, 
damaged all the rest of the brick buildings, more or less. (Plate 1104.) The damage 
done to frame houses was proportionately far less. Forty buildings were counted, 
however, that were thrown off their foundations and damaged to a greater or less extent. 
In many instances these buildings were completely demolished. (Plate 1098.) Nu- 
merous wind-mills and tanks capsized, while at least 95 per cent of the brick chimneys 
thruout the town fell. Movable objects, such as pianos, were in most cases wheeled 
out into the room, but there did not appear to be any general direction in their displace- 
ment. Water and mud in many instances are reported as having spurted from the 
artesian wells, but in a few days they resumed their normal condition. The plate-glass 
windows on the south side of First Street were cracked much more than those on the 
north side. This phenomenon was not noticeable on the other streets. 

Data were obtained of the directions in which the chimneys fell thruout the town. 
After the data were collected and tabulated as shown below, it became evident that 
chimneys usually fell with the slant of the roofs. 

In order to group the directions in which chimneys fell, the cae was divided into 8 sec- 
tors, of 45 degrees each, starting from the bearing of First Street, namely N. 30° W. 
The general directions of these sectors are: N. 15° E.; S. 15° W.; s. 75° Ev N. 75° Wee 
N. 60° E.; N. 30° W.; 8S. 30° E.; and 8. 60° W. Then the direction of the falling 
of a chimney was taken according to the sector toward which it fell. The streets in 
the main part of town run either parallel or at right angles to First Street. Since the 
bearing to First Street is N. 30° W., that of Santa Clara Street (at right angles to First) 
is N. 60° Ky. Generally the slant of the roofs of the houses that face these two streets 
will be N. 30° W., 8. 30° E., N. 60° E., and 8. 60° W., respectively. It was in these four 
general directions that the greatest number of chimneys were thrown over. The eight 
general directions are as shown on the following table: 


Directions of throw of chimneys. 


























On ago parale! pier Se ote hel 
Santa Clara Street and | imately parallel. to” First |Total number of chimneys 
percentages of total num- Street, and pty bearings thon in San ore nee 
Directions. ber down on these strects| are N. 30°39’ 45" W. their direations ot 1eiHag: 
whose bearing is N. 60° 
Sieh Percentage. pple Sel 0 Percentage. pAlb! sib Percentage. 
N. 1.57556. fie 52 7.3 222 LU, 274 10.1 
Ss. oe Wane ee 43 6.1 184 9.2 227 8.4 
5. Ft Ee eee 87 12.3 225 13 312 VELLA: 
N. 73° Wt es 69 Ler 248 12.4 317 Le 
INO Oceans 178 25.1 239 11.9 417 15.4 
NiRSO", Wi Ba 58 8.2 362 18.1 420 15.5 
: fO0° ee 82 eS 348 17.4 430 15.9 
SOP We oe 141 19.8 172 8.6 313 1 om 

















PLATE 110 


Pet ee 
Z Moved 





A. Post-office, San Jose, 





B. Box factory, corner Fifth and Julian Streets, San Jose, A.C, L, 





‘esop UBg 





sn Sears mene cain ee eo a 5 ed a Sen i RTON MPC AT Pee Wr oe 
> 
a¥ - 
{ 
j 
4 
7 
‘ 
- 
“t 
. ‘ 
\ 
i 
. 
a 
: 
' - 
< 
— 
Lh ~ ae 
. 
a 
, 
- 9 
f <= 
3 A 
z vy 
v 
~ 
: 
i 
ab a 
ri 
; 
a7 
7 
‘ in 
i] of 
ee 
¥ 
7 v 
oy*. 
7 \ 
. 7 
5 
{ 
‘ 
’ i 
tn, 
a 
i 
7 
i 
i 
% 
* 
4 
: “0% 
: 1 Le, 
' : a 
P A © , a 
Pa ha ke eto 4 
= ae NJ ] a ‘ 4 
ea 
' ? ’ 
Z 
E f 
< ¢ : a7 
’ oem 
ak 
= 
7 ) =a ss ree. 
i Cae 7 \ - 
on) PY cy : Biase 
7, me a) A" 7, * ae 





PLATE 112 





San Jose. 





; ; 
~ 
ie 
fe nee we nig ee ee nn et a» Spree ie mat se acer 
7 rm aa “> W4 \@ 
v - nt 
a ; 
‘ a 1 
et 
Fe 
a 
i+ 
ad 
- 
rt 
y 
- 
's 
‘ 
5 
: ae 
“aie 
e 
q rie 
rg 
/ al Pa 
\ 
% J 
) ' 
ry 
> 
‘ 7 me S1tee ) Say an: Me olen 
: pss voor) 
ei ; 


oon 
t 


¢ r. - x ~ ; : . 4 *- i oJ 
‘ toed 7 ; vi ae 


) 
‘ 
i 
* ‘ 
a 
+ 7 
. . J y 
nt i 0 
7 i 

f y = ane if 


113 


PLATE 


PEP 
ee 





San Jose, 





ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 285 


(Ei. C. Jones.) —There was only one broken gas main in San Jose, caused by the high 
wall of the building falling over; the bricks penetrated thru the soft earth to the main 
and broke it. At the gas station, the brick retort house was very badly damaged. The 
north and south gable ends fell out. The brick work at all 4 corners loosened for about 
10 feet down to where the roof trusses are anchored in the walls. The superheater of 
one of the gas-making machines settled on the south side so that it was 2 inches out of 
plumb. The weight of this machine is about 78 tons. Some of the cast-iron connec- 
tions in the building were broken. 

The purifying house, also of brick, was totally destroyed; all the walls and the roof 
collapsed, carrying the machinery to the ground and destroying it. The relief gas- 
holder was full of gas at the time of the earthquake and was badly damaged. Two of 
the cast-iron columns were broken off in several places; portions of the railing fell thru 
the crown of the gas-holder, permitting the gas to escape. The distributing holder 
was three-fourths full of gas at the time of the earthquake. The movement threw about 
12 inches of the water out of the holder tank. The carriages on the lower section were 
all broken, these being of cast-iron. The upper carriages, made of wrought iron, were 
strained but not broken. Considering the violence of the disturbance at this point, it 
is surprising that the mains did not suffer more than they did; but the breaking off of 
pipes in the buildings and the crushing of meters under falling houses necessitated shut- 
ting off the gas thruout the city for 24 hours. 

(W. 5. Prosser, C. E.)—Over the San Jose area, as a whole, the wreckage seems to 
have been thrown i in all directions; but in certain places some slight system appears. 
It seems clear that no statement as to direction, amount, or even duration of motion 
applies to more than a limited area. The only clear cases of rotary motion seen by me 
were two cases near my home, 2 miles northwest of the centerof town. One tank-house 
turned exactly halfway round, as well as upside down, and one chimney turned about 
4 inches, both in the direction of the hands of a clock. Both rotary and vertical motions 
were felt by many, however. About 500 yards from me is a square brick fence-post 
7 feet high, of which 2 feet moved about 3 inches to the southeast (S. 44° E.); or rather, 
the bottom moved the reverse way. On Stevens Creek road, leading southwest from 
San Jose, 5 or 6 water-tanks on the roadside fell. One of these seemed thrown to the 
northeast, but others were twisted and scattered as tho by a mixture of all motions. In 
some places most of the buildings, perhaps, fell to the north or northwest. In China- 
town (north of San Jose) it was the north and south brick walls that fell. In San Jose 
most of the clocks on east and west walls did not stop, but many of those on north and 
south walls did; showing an east and west motion. The brick 7-foot wall around the 
yard of Notre Dame School in San Jose, on the northwest side, fell; but that on the south 
did not, altho it was cracked. - The streets in the central part of San Jose run N. 60° E 

The amount of motion differs greatly. In many cases brick work seems to show a 
sharp blow of 2 inches; sometimes more. The inside east and west wall of the City 
Hall has a crack of 4 inches. The front of La Mott House (east and west) moved in 
some places 2 inches, in others 4 inches. The master clock in the Western Union Office 
(on the ground floor of a large brick building, and on the east and west wall) did not 
stop, but the pendulum struck both sides of its case many times and with great violence, 
battering off the varnish. It is long (probably beats seconds) and had to move about 
4 inches more than usual in order to strike the case. 

About 5 miles south of San Jose there were said to be two tubs of water on the ground 
afew hundred yards apart. No. 1 had most of the water splasht out, but No. 2 ap- 
parently had lost none. No. 2 is nearer the hills, and bedrock is nearer the surface. 
The oil tank at the corner of Stockton and Polhemus Streets, 1 mile northwest of San 
Jose, splasht over. Many water-tanks did the same. 


286 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


Several good observers out of doors are positive that the noise of the quake came from 
the southeast and died away toward San Francisco. In the afternoon of the 18th, my 
wife heard the noise of a shock and called out before we felt the shock itself. The noise 
seemed to come from the south or southeast. 

Many persons saw waves in the ground. Sifting out exaggerations, these appeared 
to be rather more than a foot in height. The best observer estimated the distance from 
crest to crest at 60 feet, others at much less; but I think the waves must have been 
greater, for there is no evidence in long brick walls showing any such vertical cracks as 
would have been produced by short waves. 

Six miles southwest from San Jose, a good observer described the waves as parallel 
with certain tree-rows which are northeast and southwest, and stated that the waves 
moved from him at right angles to the line and toward San Francisco. Six miles north- 
west from San Jose, a man looking south saw the waves (which he thinks were east and 
west) coming toward him, and hence toward San Francisco. About the middle of 
the quake these were met by other waves, and the whole surface resembled hillocks, 
or cross-seas, while the tree-tops waved wildly. To the man southwest of San Jose, 
however, the tops of the trees were almost still, while the trunks waved sinuously. Near 
me is a piece of ground 10 by 30 feet, raised about 7 inches; while about 150 feet south- 
east of this is an area about a yard square which dropt 6 inches. Possibly these repre- 
sent the crest and trough of an earth-wave. 

I estimate the duration, I think closely, at between 50 and 60 seconds. 

The wells of the vicinity seem to show slightly increased flow. One 80 to 100 feet 
deep has been a little roily since the quake, and one near San Jose was reported as having - 
increased the day before the quake. 

(M. Connell.) —On the farm of Mr. Fox, 3 miles north of San Jose, the water pipe of 
an artesian well was broken off 60 feet below the surface and carried by the heave of 
the land in a northwesterly direction 4 feet from its original position. 

County road south of San Jose (H. R. Johnson). — At Schutzen Park, 2 miles south- 
east of San Jose, the shock was felt quite severely. The road house was badly shaken, 
but very little glassware was broken in the bar-room. A 12,000-gallon water-tank was 
shifted slightly on its foundations. At this place the first part of the shock was thought 
to be quite light and the second part heavy; the general motion was said to be from east 
to west. At the 5-mile house, farther southeast on this same road, there was hardly any 
damage reported. Even plaster in houses did not fall. Thére was also little damage 
at the house 0.5 mile southeast of the 5-mile house. The chimney did not fall, but 
dishes and lamp-shades were broken. The movement was thought to be northwest- 
southeast in direction. 

It was stated by Mr. Russel, of Edenvale, that the shock was lighter there than at 
San Jose. A well-constructed brick building, which was built 3 years ago, had the 
roof loosened and the end walls were cracked. About 3.5 miles southeast of the 5-mile 
house at the Van Every ranch, a chimney fell, plaster on the first floor was badly 
cracked, and furniture slid around upon the floor. Water was spilt from a tank and 
a water-trough. 

Just northwest of the 12-mile house, where the county road crosses to the Fisher ranch, 
there were cracks from 2 to 6 inches wide in the coarse gravelly bottom of the Coyote 
River. There was evidence of water having been ejected from these cracks, as there were 
heaps of clean, fine material surrounding small orifices. It was said at the ranch-house 
that muddy water came out of these openings following the shock. Half a mile south- 
east of Fisher’s, a water-tank was down. 

Half a mile south of the 15-mile house, the Barnhart ranch-house, which was set upon 
wooden underpinning, was thrown from its foundation, so that it rested directly upon the 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 287 


ground, 4 feet farther north than its proper place. An old barn and water-tank were 
uninjured at this same place. 

A quarter of a mile south of the 15-mile house, on the county road, a water-tank was 
thrown down. Going 38 miles northeast from the 15-mile house, Webber’s old ranch- 
house was visited. Here baled hay piled in a barn was shaken down and doors leaning 
against the house were thrown from their position. Water in both the creek (Coyote 
River) and a well was muddy after the shock. 

(H. R. Johnson).— Going northeast thru San Felipe Valley to Smith Creek Hotel, 
hardly any evidence was seen of damage from the shock. At Smith Creek Hotel no 
china nor plaster was broken, but two chimneys were thrown down. 

Los Gatos to Gilroy (G. A. Waring). — Near Meridian, 3 miles west of San Jose, several 
cottages were shifted from their foundations. All water-tanks on open frames fell, but 
those that were boarded in stood. The water became muddy in several wells. One 
lady reports seeing waves traveling southward along the driveway, and a man reports 
seeing a heavy wagon move 4 or 5 feet back and forth several times, along the driveway. 
The shock began violently and ended suddenly. The intensity diminished uniformly 
from Meridian toward Campbell. At Campbell, 68 per cent (51 out of 89) of the chimneys 
fell, but the plastering in the houses was not badly injured. From Campbell toward Los 
Gatos the intensity slightly increased. At Los Gatos 78 per cent (67 out of 86) of the 
chimneys fell. At the distillery 4 miles west of Los Gatos considerable damage was done. 
The second floor was moved about 18 inches toward the northeast, causing the wall to 
bow out on the northeast side. Many of the large vats holding 2,000 gallons were shaken 
off their supports and several were broken by the fall. The shock in Los Gatos, however, 
was not so sudden as to cause serious injury to brickwork or plastering. The business 
part of the town is built on 40 feet of gravel overlying shale. Only two stones in the 
Los Gatos Cemetery were shifted. 

At Alma the shock was of about the same intensity as at Los Gatos. Milk in pans 
was nearly all thrown to the north and south. The Morrell house (see plate 1078), 
near Wright Station, is directly over the fault and suffered more than any other place in 
the vicinity of Wright Station, tho at least 5 other buildings between Patchin and Sky- 
land were badly wrecked. Going from Los Gatos toward Edenvale, the shock was some- 
what lighter than at Los Gatos, judging by the effect on chimneys, plastering, and mov- 
able objects; but at Edenvale it was a little stronger than at Los Gatos, as shown by the 
damage done to the large brick canning factory. All the walls were badly cracked and 
the tops of the walls fell. The top of the fire-wall above the roof was shaken down. 

Continuing to the southwest thru Coyote, it was about the same as at Los Gatos, 
diminishing a little thru Madrone, Morgan Hill, and San Martin, where it had about the 
same intensity as at Los Gatos. Near Coyote aman reports having seen a northwest- 
southeast fence move in wave-like fashion, beginning at the southern end; and he heard 
a noise coming from the southeast and seeming to pass over him. Another man driving 
along the road near San Martin, heard a roar and his horse became frightened, before the 
shock came. Clouds of dust arose in the road and the creek near by was rendered muddy 
by the shock. At Morgan Hill about 64 per cent (18 out of 28) of the chimneys fell, 
and a 1-story concrete-block building was badly damaged, the whole front having fallen 
out. A 2-story reénforced concrete-block building was not damaged. 

At Bucker, 3 miles north of Gilroy, the shock seems to have been about the same. 
The school building was badly damaged, and several windows were broken by the twisting 
of the frames. At Gilroy nearly every chimney fell, fire-walls of brick buildings were 
thrown down (plate 114A, B), and shelf goods were largely shaken down. In the Masons 
and Odd Fellows Cemetery, out of 120 stones over 3 feet tall, 31 fell. A cylindrical shaft 
fell north, and a square one fell south, but all the rest fell east or west, tho the tall slabs 


288 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


necessarily fell east or west because they faced east. Two marble shafts about 8 feet 
high were broken off halfway up, the lower part and base being unshifted. In'the Cath- 
olic Cemetery 10 stones out of 67 fell. 

In the hills between Los Gatos and Gilroy the shock seems to have been somewhat less 
severe. At the New Almaden mines, the tops of 2 brick furnace chimneys, about 50 
feet tall, were broken off; but the furnaces were unharmed and the underground work- 
ings unaffected. About 70 per cent (16 out of 23) of the chimneys in the settlement here 
(Hacienda) were broken off. A loud noise like thunder is reported to have traveled north- 
ward down the canyon, distinctly preceding the shock. This has often been heard since, 
seemingly underfoot, even when no shock has been felt. 

Southward from New Almaden thru the hills the houses on alluvial land suffered notice- 
ably more than those on more solid ground. From Uvas westward to the summit, the 
intensity rapidly rose as the fault was approached. ‘Two miles west of Uvas P.O., and 
half a mile east of the summit, an east-and-west stone wall, built of loose boulders, was 
thrown mostly northward; water was thrown from troughs toward the north; and all 
streams were muddy for 2 days after the shock, while in wet places there was a noticeable 
settling of the ground. 

Southward from New Almaden along the eastern side of the valley, the shock uniformly 
lessened in its intensity thru Old Gilroy and San Felipe to Hollister. At San Felipe a 
large stone cheese factory was not damaged, except for a few cracks. The lake 0.5 mile 
west of the village was considerably stirred up, and water from a full road tank was thrown 
60 feet across the road. A considerable rumble was heard all thru this region; one per- 
son says it came from the southeast, traveling down the valley; another says it came from 
the southwest. 

Along the railroad track from Gilroy to Sargent, nearing the fault, the intensity rose 
considerably, but the motion was a slow, swinging one. Water was all thrown from 
reservoirs, and trees swayed violently; but plastering and shelf goods suffered little. 
At Sargent all loose objects were thrown about, but no buildings were shifted. 

(A. J. Champreux.)—About 90 per cent of the chimneys in Gilroy fell, the prevailing 
direction being east and west. No frame houses were thrown off their foundations. 
Brick walls were damaged at the top by the fall of 8 to 20 courses of brick. Most of the 
plastered houses suffered by the cracking of plaster. No cracks were found in roads or 
pavements. At the Cemetery, about 50 per cent of the monuments were overthrown. 
Of the fallen ones, 95 per cent were thrown in an east-west direction. All monuments 
overthrown had square bases. 


HOLLISTER TO PRIEST VALLEY. 


Hollister (G. A. Waring). — At Hollister (plate 114c, p) the chief damage was to the 
Grangers’ Union, the Rochdale store, the Catholic school, and the fire-house. The two 
stores were poorly built, however, with large rooms unsupported by partitions or columns, 
while their shelves were heavily laden with goods. The school was on tall underpinning, 
very slightly braced, which allowed the building to lurch northward and settle to the 
ground. Unsupported parts of the fire-house walls (2 bricks thick) fell outward, but the 
portion braced by posts and tie-rods was unhurt. Sixty-five out of 123 chimneys fell, 
or 58 per cent. Several locked doors were thrown open, in one case the bolt being broken. 
One old settler remembers when the business part of Hollister was a slough. An artesian 
belt also passes thru the town, which may have affected the intensity along its path. 

(A. J. Champreux.)— Practically all chimneys fell, the prevailing direction being east- 
west. _ One frame house, “School of the Sacred Heart,” 2-story, was completely wrecked. 
The foundation gave way in the front part of the house, allowing the floor joists to drop. 


114 


PLATE 








A. Gilroy, 


C. Hollister. Demolition of brick building shown in D. Blakesley, Photo. 


1D. THoRy 











TUNG 


D 








Hollister. Same building as shown in C, before earthquake. Blakesley, Photo. 





ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 289 


This house was on the outskirts of town and on sandy soil. No other frame house was 
damaged. Two brick buildings, of poor construction, collapsed. The outer walls gave 
way, allowing the interior to drop. 

(James Davis.)—Two shocks were felt, of which the second was the stronger. There 
was an interval of 3 or 4 seconds of less motion between these maxima. A rumble pre- 
ceded the shock by a second or so. In my house a piano and other heavy objects were 
moved on a polished floor so that the north ends moved 2 or 3 feet out into the room 
farther than the south ends. I was standing at the time of the heaviest shock, and was 
thrown from side to side in a north and south direction. People here all agree as to the 
north and south direction of the movement. Most chimneys fell north, but some fell 
east and west. Pictures on east and west walls, hanging by single wires 4 to 6 feet long, 
swung from 3 to 8 feet along the walls, leaving distinct scratches. Pictures similarly 
hung on north and south walls simply pounded back and forth, leaving punctures in the 
plastering. Water-tanks seem to have fallen to the north always. Three brick buildings, 
each 2-story, 1 old and 2 new, went down flat, and 2 others were badly damaged. Wooden 
buildings in general were not damaged except thru the fall of chimneys. The Catholic 
convent, however, was injured. 

There were no changes in the ground at Hollister save some slight cracks in the vicinity ; 
but a small peak near Santa Ana showed a landslide down its steep face, plainly visible 
at a distance of 6 miles. A huge rock, rolling down a hill in Santa Ana Valley, crashed 
thru a house and killed a man. 

(J. N. Thompson. )—All brick buildings were destroyed or badly damaged. There were 
2 shocks, lasting in all about 50 seconds. The first appeared to be north and south, and 
the last part of the second shock appeared to be a twisting motion or a change to an east 
and west motion. My chimneys fell first, and nearly to the south; then at the last 
motion my wind-mill and tank fell to the west. The most damage was done at the close 
of the last vibration. A sideboard against a north wall was moved several inches to the 
south, and a clock on the same wall was thrown to the south. A bed against the west wall 
moved several inches to the east. 

From Hollister to San Benito (G. A. Waring). — The effect of the shock upon alluvial 
soil is very noticeable. In the hills toward the Stayton Mines the shock was so feeble that 
it was not noticed by some people. Thru Brown’s, Los Muretos, and Quien Sabe Valleys 
it was generally only sufficient to throw the cream from pans of milk. The often repeated 
story of the man who was killed in Quien Sabe Valley, by a rolling boulder crushing his 
house, is not to be accepted as a measure of the intensity. Several loose rocks were 
shaken down in the neighborhood of Santa Ana peak, and springs increased their flow ; 
nevertheless the shock was very light. 

At Palmtag’s winery, in the hills southwest of Tres Pinos, the shock seems to have been 
more severe than elsewhere in the vicinity of that village. Furniture was moved, water 
was thrown from troughs, and an adobe building was badly cracked. One low brick 
winery was unharmed. A distinct rumble preceded the shock; 2 distinct periods were 
felt and the shock seemed very long. There is a small lake on the Palmtag place, and 
the ground seems rather marshy. Possibly this had some influence on the intensity, tho 
there is reason to believe that the projection of the fault passes thru the hills in the im- 
mediate vicinity. 

At Tres Pinos, out of 18 chimneys only one fell and it was unstable. Shelf goods were 
almost unaffected. There is hard rock (sandstone or shale) in place, however, at a 
depth of 2 to 4 feet, at Tres Pinos. 

Paicenes, tho south of Tres Pinos, was more violently shaken, for it stands on gravel. 
Milk and water were spilt somewhat, and a few tall bottles were thrown from the shelves. 


Water is said to have spouted up in the flat land along the river, 0.25 mile from the stream. 
U 


290 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


Toward the Cienaga lime-kilns the intensity lessened considerably. One man in the 
foot-hills 4 miles southwest of Paicenes, reports seeing a wave coming westward thru a 
grainfield, and some oaks waving considerably ; but he did not hear nor feel any shock. 
Four miles southwest of Paicenes, a hanging lamp swung strongly east and west, and milk | 
was spilt from the pans. At the kilns, in a granitic region, tho a distinct noise is said 
to have preceded the shake, only one slight shock was felt, and that was not sufficient to 
spill water from a full bucket standing on a table. Along the river between Paicenes and 
Mulberry, a distinct vertical motion is reported, causing weighted windows to be thrown 
up and down, and stove-lids to dance about. Liquids were strongly affected, as were 
trees and hanging lamps, and a few articles were thrown from shelves. 

On the afternoon of June 13, a lady near Mulberry, 5 miles south of Paicenes, was 
talking over the telephone with a friend in Hollister. The latter suddenly gave a startled 
ery as a slight earthquake shock occurred. It was felt at Mulberry several seconds later. 
From Mulberry to San Benito the shock uniformly lessened until, at the latter place, 
altho distinctly felt, even liquids were not disturbed by it. 

Thru Bear Valley the only noticeable effects of the shock were the swinging of lamps 
and the disturbance of water surfaces. Little or no sound was heard in Bear Valley, but 
several people noticed 38 distinct periods of vibration. It began easily, rapidly increased, 
and then, after a pause, there came a harder shake. At one house a lamp hanging bya 
chain 3 feet long is said to have swung north and south nearly to the ceiling. Articles 
on shelves were not moved, nor loose window lights shaken out. At the summit at the 
south end of Bear Valley, about a bucketful of water was thrown from a barrel only two- 
thirds full, and cream was thrown north and south from pans of milk. Here also the hang- 
ing lamp swung strongly north and south. A man outdoors became dizzy and nauseated, 
but did not at the time realize the cause. 

Thru the south end of the valley, hanging lamps are said to have swung east and west, 
and water is said to have spilt mostly east and west. Several people became dizzy, 
but the motion seems to have been too slow to be distinetly appreciable. 

At the Pinnacles no loose rocks were displaced, so the movement must have been slight. 

Traveling southeastward from San Benito up the valley toward Hernandez, the motion 
consisted of longer, slower vibrations, and was of remarkably long duration. In general, 
the effect was only to set rocking-chairs in motion, cause doors to swing, and trees to sway. 
Just south of the divide between San Benito and Hernandez Valleys, the intensity rose 
noticeably, the shock throwing a lamp and clock from a shelf. 

At Hernandez, pans of milk and troughs of water were almost emptied, and many minor 
shocks have been felt since. No noise was heard before the quake, but a report as of a 
blast immediately preceded the second (hardest) period of vibration. This is in an upland 
valley at 2,500 feet elevation, but the ground seems to be full of water. 

In the mountainous serpentine area between Hernandez and New Idria, the shock 
was evidently slight, as nothing was noticed to have been disturbed at Smith’s camp. 
At New Idria a few bottles and light articles were thrown from shelves, clocks were stopt, 
and a few bricks loosened from a building erected with mud mortar; but chimneys were 
not injured. One brick furnace was cracked, but it was not properly braced. Only 3 
minor shocks have been noticed at New Idria. The intensity was about the same as 
at Hernandez. 

In Vallecitos Valley, at an elevation of 2,000 feet, Tertiary rocks are overlain by 50 
feet or more of alluvium. In this valley, pans of milk were slightly spilt, but nothing was 
thrown from shelves. 

From San Benito southward thru the Bitterwater Valley, the intensity lessened, 


and only liquids were affected. The motion was too slight to be appreciable to some 
people. 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 291 


Priest Valley (D. 8. Jordan). — On May 18 I went to Priest Valley, in the southeast 
corner of Monterey County, 37 miles east of King City. I had heard that rumblings 
were frequently heard in the valley, and that people were moving out on account of 
them. There was little trace of the earthquake at King City. At Lonoak, 16 miles 
east, chimneys were thrown down and a mild earthquake was felt. At Priest Valley, 
which is near the line of the old fault and at the very foot of the main range of the Ga- 
vilan, the earthquake shock was very severe, apparently coming from the north. Chim- 
neys were thrown down, dishes were broken, and the contents of the store thrown over 
the floor. Rumblings were alleged to have been heard by a man named George Brew. 
He had been hunting in the mountains, and said he had heard noises like cannonading 
in the ground at night. This was before the great shock. 

There were slight landslides and cracks along the edge of the creck banks. There 
is, however, no trace of the great crack in the valley. No one had seen it cross the stage 
road; and the oil pipe line from Alealde, in Fresno County, goes thru to the Salinas 
Valley without any break. The people said to be moving out of the valley were two 
frightened women up in a mountain gorge, whose husbands had gone to look after friends 
in San Jose. It is evident that the main crack did not reach as far as Priest Valley, and 
the shock at that point was not very different from that at San Jose, except that the 
blow was more direct, with less twisting motion. 


MONTEREY BAY AND EASTWARD. 


Pacific Grove, Monterey, and Del Monte (A. 8. Eakle). — At-Pacifie Grove very slight 
damage resulted from the shock, altho according to residents the vibrations were very 
severe, in a northeast to southwest direction. Only one or two houses had chimneys 
cracked, tho there are several massive chimneys, some with heavy ornamental tops. 

The town is situated on massive porphyritie granite, and the overlying soil is not deep. 
Its situation was evidently the reason for the slight damage done. The Pacific Grove 
light-house is situated about a mile southwest and this showed more severe effects. The 
lamp is enclosed in a ribbed metal frame which rests on a brick tower and dome. The 
vibration of the ribs caused them to strike the metal chimney in the center of the top 
and dent it on the easterly side. The motion of this upper portion caused the brick dome 
supporting it to crack immediately at the base of the curved dome. There was no 
displacement of bricks, the crack being a fine one, visible both within and without the 
tower, and completely encircling it. The light-house is built on a sand-dune and there is 
an estimated thickness of 80 feet of sand upon the underlying rocks. This sand founda- 
tion probably accounts for the apparently greater intensity of the shock here than in 
the town. Some of the objects in the rooms of the house were also slightly misplaced. 

Judging the intensity of the earthquake by the damage it did in Pacific Grove, it would 
probably be classed as VI in the Rossi-Forel scale, as it was severe enough to awaken 
practically every one, tho no windows were broken, so far as could be ascertained. 

Monterey experienced practieally the same intensity. I could learn of no damage 
done to the houses, the only damage reported being of some glassware in a few stores. In 
some houses furniture was moved slightly, and top-heavy pieces were overturned. This 
town, like Pacific Grove, is on a good rock foundation; but in places the sand is deep. 

Del Monte suffered the most, as practically every chimney of the hotel was cracked or 
thrown. There were over 50 chimneys in the hotel, and half of them were thrown down ; 
one crashing thru the roof on the west side of the hotel and causing two fatalities. The 
chimneys were tall and top-heavy, having ornamental tops; and while the damage to the 
interior of the hotel was very slight, showing that the earthquake was not of a violent 
type, the vibrations were sufficient to throw these top-heavy chimneys. The hotel is on 


292 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


alluvium, and the grounds surrounding it are in part “made” land. The grounds are 
surrounded by marshy land, ponds, and sand-dunes, and there is evidently a considerable 
depth of an incoherent, water-saturated formation supporting the hotel; this probably 
explains why Del Monte suffered so much more than Monterey. The houses adjoining 
the grounds were not damaged, with the exception of the school-house, which had its 
chimney cracked at the base. 

On the road eastward to Salinas from Del Monte, no visible signs of the earthquake 
were encountered until the Salinas River was reached. The Salinas bridge was moved 
southerly several feet, according to report, and the framework was broken so as to 
render the bridge unsafe. The bridge farther down the stream, on a wagon road from 
Castroville railroad station to Monterey, was also damaged by the shock. This bridge 
crosses the river in a northeast to southwest direction, and is supported by four tiers of 
piles, boxed around with plank. The two end piers were not misplaced, but the two inter- 
mediate series were bent or broken at their bases and shoved over to the northeast, caus- 
ing a sinking in the center of the bridge of about 2 feet. The damage to the bridge was 
due to the violence of the shock, and not to a sinking of the ground, as the amount of drop 
in the center was equivalent to the slanting position of the two intermediate supports. 

Castroville to Soquel (G. A. Waring). — Castroville, being on solid ground, was not 
seriously affected. Three chimneys out of about 30 fell. Objects were thrown mostly 
westward. The quake was described as beginning like a subterranean blast. Two 
periods were not noticed; it was felt as one continual vibration, starting very gently. 

The wharf at Moss Landing buckled up and partly collapsed, while the warehouses were 
wracked or fell westward. (Plate 116p.) At the hotel and stores on the mainland, brick 
chimneys fell, but plastering was not seriously cracked. 

At Watsonville about 90 per cent of the chimneys were broken off at the roof-line, the 
greater portion being near to the river. Several were cracked and twisted but not thrown 
down. Parts of a few brick walls near the river fell, and considerable settling of the 
ground took place in Chinatown on the southern side of the river. (Plate 116a.) 

On the higher ground between Watsonville and Aptos, the shock was little felt. There 
was no movement along Aptos Creek, both wagon and railway bridges being unaffected. 

In one old house about half the plaster was thrown from every northern and southern 
wall on the first floor, but not from the others, nor from the upper rooms. A bureau 
was moved eastward 3 feet from the wall, but no other furniture was moved. 

Nearly all the chimneys at Capitola fell, and considerable plaster was shaken from the 
north walls of the first floor of the hotel. The vibration is said to have been almost en- 
tirely east and west, as shown by the sash locks having been broken only upon the east 
and west windows. An iron safe free to move northward was unmoved, but the plaster 
on the opposite side of the wall back of it (west) was broken. A case of pigeon-holes 
resting on top of the safe slid to the east edge, when it could as easily have moved north. 
Much earth fell from bluffs near the town, but there was no appreciable effect on the 
surf. At the country bridge across Soquel Creek, the ground at the east abutment shoved 
inward, cracking the concrete and buckling a water-pipe. 

In the low ground at Soquel, nearly all the chimneys fell, but most of those on high 
ground stood. Much plaster fell and goods were thrown from the shelves in the business 
section, which is close to the creek. The east abutment of the concrete wagon bridge 
over Soquel Creek cracked vertically, showing that the soil movement extended this 
far up the creek. Thru Delmar, Seabright, and Twin Lakes nearly all the chimneys 
were either down or twisted part way around and left standing, an unusual number being 
thus twisted. The shock is said to have come suddenly, diminished, and then, at a second 
jolt, chimneys fell. Trees moved sideways as well as swayed, and all animals were much 
frightened. One small stream has diminished in flow. 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 293 


(D. Stirling.)—In the Pajaro Valley, on the McGowan ranch, at a bend of the river, 
an acre or more of orchard has sunk about 2 feet. At Moss Landing, where the river runs 
parallel with the shore line, the strip of land is seamed for miles. A crack, or rather a 
sink, about 20 feet wide and 4 or 5 feet deep ran under the buildings and rent them 
asunder. The office building between this crack and the river has been moved 
bodily — land and all — about 12 feet toward the river. Some of the cracks run into 
the ocean. At Neponset and Salinas the piling under the county bridges was moved in 
some of the bents at least 10 feet toward the river. A section man who stood in the midst 
of the cracks at the end of the Neponset bridge was drenched with spurting water. 





SALINAS TO SAN LUIS OBISPO AND WESTWARD. 


Effect of the Shock on Alluvium (G. A. Waring). — Altho the Salinas river bed sank 
nearly 6 feet at King City, and the wide sandy bottom at Three Mile Flat was much 
cracked, the southernmost extension of continuous cracks along the bank was found to 
be about 2.5 miles south of Gonzales bridge. From here to the mouth of the river the 
cracks are parallel with the river banks. 

The movement at Gonzales bridge was mostly on the west bank of the stream. A wire 
fence trending north and south was torn 6 inches apart here, and wooden piles at the 
southwest end of the bridge, said to be driven down 75 feet, have been torn loose and 
moved from plumb, their original upright position. At the northeast end of the bridge 
the piles are undisturbed, but the surface soil and a wire fence have moved relatively 
18 inches northward. (See fig. 59.) 

North of Gonzales bridge the fissures are mostly on the west side of the stream channel, 
and reach a maximum width of 18 inches. No evidence of shearing could be found. In 
the creek bottoms west of Chualar, sand craterlets begin to appear and become numerous 
along the stream northward. 

Near Agenda, in the lowlands, is a cracked area nearly a mile from the river, probably 
along an old water course; while sand craterlets are scattered thru the orchards. At 
Spreckels the movement caused much damage to flumes, sewers, and water-mains; and 
from here to Blanco the deep soil of the adjacent fields is much cracked and in places 
sunken and dotted with sand craterlets. 

The county bridge south of Salinas was rendered unsafe by the movement of the piers 
at the southern end. (Plate 123.) On the west bank near the bridge a series of peculiar 
eracks have torn up the road and adjacent field, along what is probably the path of an old 
water course. These are shown in plates 136, 137. ; 

Between Blanco and Neponset the cracking and settling of the low land flooded the 
adjacent fields and gave rise to stories about the Salinas River having risen several 
feet. The “boiling up” of the water thru sand craterlets was also soon distorted into a 
story about the water of the Salinas River being boiling hot. Both the railway and 
county bridges at Neponset were moved, the northern concrete piers of the former 2 
inches east and the central wooden pier of the latter apparently 4 feet south. 

From Morocoho to Moss Landing fissures rarely show in marshy land, but the narrow- 
gage railway track has been shifted a few inches in several places. At Moss Landing 
many small cracks occur in the mud on the west side of the river, and the condition of 
the wharf indicates an eastward movement of the sand-spit. (See plates 1348, 135A, B.) 
It is reported that at places along the pier where the water was formerly 6 feet deep, it 
now has a depth of 18 or 20 feet. North of Moss Landing the ground settled nearly 2 
feet in places, as shown by marks on railway piles at several slough crossings and by the 
sagging of the track below grade line in several other places. The stretch of narrow-gage 
track parallel to the coast has been disturbed for nearly its whole length; in some places 
it is wavy, in others the entire roadbed has shifted. At one point about 5 miles south of 


294 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


0 
oO 
is) 

o 





CONSTRUCTION OF PIERS 





t = vt 
COP Ses | 


I rit 
! ae H 
I 1 i H 
' P ' 
' ' 
i 7 : 
a J 
4 ae ” 
South edge of stream 


LOATY SOULJVS: ——> 








Wire fence 





“ 
====7 


«+ North bank of channel 


12' Piles 


12"x 12" Cap 


2” Plank 





CONSTRUCTION OF PIERS 


The bridge is } mile long. 


Fic. 59. — Displacement of piers of highway bridge across Salinas River, 3 miles west of Gonzales. 


Watsonville, where the railroad track is only about 
200 yards from the beach, a stretch 100 yards long 
running northwesterly had shifted a maximum of 12 
feet to the northeast. Fences, telephone poles, and 
track all moved together. The sand-dunes facing the 
beach directly opposite the place where this movement 
occurred look as if they had been struck by a single 
large wave. 

Cracks appear again along the Pajaro River and the 
railway track has sunk in several places. The side 
rods of the narrow-gage bridge 1 mile south of Watson- 
ville are buckled as by a compressive force, and the . 
roadbed at both approaches has settled at least 2 
inches. 

Continuing up the Pajaro River, evidence of settling 
is found at the broad-gage railway bridge at Watson- 
ville, the southeast end of which sank more than a 
foot. The track was also twisted into an §-shape. 
The concrete foundation under the engine and stack 
at the power-house at the northwest end of the bridge 
settled, but the concrete work was little hurt. In 
Chinatown, on the south side of the river, the settling 
of the ground was marked. 

Between Pajaro and Vega the ground cracked along 
the 2 to 6 foot bluff, marking the old river bank on 
the south side of the present channel, and the side 
toward the river has settled several feet. This is 
well shown in plate 1418. This displacement has 
caused numerous sand craterlets and pits (plate 
1438); the largest pit noted being oval in shape, 6 
by 20 feet in diameter, and 4 feet deep. Northeast of 
Vega the movement,seems to have died out, the last 
evidence found being mud caps on some old piles in 
the channel of the stream, showing a settlement of the 
ground amounting to 8 inches. Between Vega and 
Chittenden no evidence of movement of the river-bed 
could be found. Near Chittenden the banks are caved 
in. Along the San Lorenzo River, at Santa Cruz, this 
settling action also took place for a mile or more up- 
stream from its mouth. 

It may be said, regarding the soil movement along 
these streams, that along the Salinas River from Gon- 
zales to near Blanco, everything shows a movement 
down the river. From Blanco to Neponset the move- 
ment seems to have been a settling of the alluvial 
materials, while from Neponset to the mouth of the 
Pajaro River the ground (in several places, at least) 
moved eastward or inland. Accepting as correct the 
reported lengths of piling at bridges, and depths at 


which the sand thrown up is said to have been found, the plane of movement must 
have been about 90 feet below the surface at Neponset, diminishing to possibly 8 or 


PLATE 115 





A. Alvarado. Wreck of molasses tanks, Alameda Sugar Company. E, W. B. 


Ai il J U 


B. Salinas. Wreck of corner store. G. RB. B. 





5 
\ 
F 
' 
a é 
OF LLINUIS 
i 
\ 
. oF : 
te4 tole mn Gy 
ES fea & : A ote Va 





ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 295 


10 feet at Gonzales bridge and ending about 2.5 miles south of it. Along the Pajaro 
and San Lorenzo Rivers the movement was a settling of the alluvial bottom-lands. 

(A. S. Eakle.) — The effect of the earthquake upon the alluvium was well shown along 
the banks of the stream from the Salinas to the Gonzales bridges. Along the east side 
of the river for a short distance south of the Salinas bridge, 4 miles south of the town, 
the land is cracked at the edge of the bank, the cracks paralleling the course of the river; 
but comparatively little cracking was observed on this side of the river. Along the 
bank and down in the river-bottom itself, on the western side of the stream, fissures 
were very prominent. The county road southward from the Salinas bridge runs along 
the embankment’ about 10 to 20 feet above the stream bed. The road is an oiled one, 
and the oil had formed a hardpan upon the underlying sand. In the vicinity of the 
bridge the road has been shattered by the quake for a distance of 200 yards. The breaks 
are in the nature of a caving in of the road on the north side of the crack, as if hollow 
spaces existed beneath, leaving a vertical escarpment on the south side. The main 
sinking is at the most southerly fissure. Here the road has sunk bodily to a depth of 
10 feet, leaving a high vertical bank diagonally across the road, and this sunken area 
extends for some distance into the adjoining field on the west. There is no upheaval 
of the road in any place to compensate for the sinking. 

South of the Spreckels factory, the low bottom-land between the banks of the river 
is considerably cracked, although there is no prominent vertical dropping of the land 
along the cracks. ‘This low land lies west of the present course of the stream, and is 
intersected by sloughs and former water courses. All of the ground is of a deep sandy 
nature, consequently it was much disturbed and fissured by the quake, and the fissures 
became filled with water and sand, forming a quicksand, this wet sand frequently being 
spouted into the air. No one noticed gases coming up. The position of the cracks is 
now marked by patches of light, bluish-gray sand in the field, from the drying out of the 
quicksands. Houses on this low land were thrown out of plumb, and chimneys were 
destroyed. The cracks diminish in number as one goes southward, and practically 
end in the vicinity of the Gonzales bridge. The quake at Gonzales can hardly be placed 
at more than VII in the scale, as comparatively little damage was done to the town. 

Effect upon structures, objects, etc. (G. A. Waring). —It is remarkable how closely 
the disturbance followed the river channel throughout the Salinas Valley; 2 or 3 
miles away from the stream on both sides the intensity was very slight. Southward 
up the valley the shock gradually lessened, and rapidly died out in the foot-hills on 
either side. 

In the hills between San Juan and Natividad the ground is not cracked, except for 
a few places on hillsides where there was some sloughing off. The shock was sufficient 
to throw nearly all the milk from the pans, but not strong enough to move furniture or 
shelf goods. At Natividad, in the foot-hills, the shock was of about the same intensity. 
At Santa Rita the shock was light; a little milk was spilt from pans, but several tall 
slender chimneys were unhurt. 

Prunedale (H. H. McIntyre). — Nearly every chimney was thrown down. All the 
goods in the store were thrown to the floor. The house was badly wrecked. Water 
started flowing in many places where there had been none, or but little, before. T here 
were 2 small landslides from springy places, the direction of the slip being from north 
to south. 

Salinas (G. A. Waring). — At Salinas 423 per cent (278 out of 655) of the chimneys fell. 
A brick store was demolished by the collapse of the roof (plates 115s, 1168), and parts 
of a dozen or more brick walls fell. (Plate 116c.) Shelf goods were shaken down, and 
a few heavy articles, such as slot machines, were overturned. Heavy furniture, such 
as pianos and billiard tables, was not moved. But little plate glass was broken. In 


296 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


some buildings plastering was badly cracked and shaken down, but in solid, well-built 
residences it was little hurt. The court-house and high-school buildings, within a block 
of each other, furnish striking examples of the need of considering construction when 
trying to gage the intensity of the shock by its effect on buildings. In the former build- 
ing the principal damage consists of a few cracks in the plastering and foundations, 
while in the high-school building a part of the front wall fell out and the roof spread 
badly, cracking the corners of the house. 

(A. S. Eakle.)—The town of Salinas suffered greater destruction than any other place 
in the county. Nearly every house and building were damaged to some extent. Plaster 
fell, windows broke, chimneys fell or were cracked, and brick buildings had their upper 
portions thrown off and, in some cases, almost completely demolished. The town is on 
the flat valley land, about 3 miles east of the river, and came within range of the more 
violent vibrations, in addition to being on alluvium. 

Spreckels and vicinity (G. A. Waring). — The village of Spreckels, on the river-bottom, 
was badly shaken. Nearly every one of the approximately 50 chimneys in the settle- 
ment fell, as did also a large part of the plaster in the 3-story hotel. On the first 
floor of the hotel building nearly all the walls were stript, but the plaster fell mostly 
from the south wall. On the second floor the walls of the north end and west side suf- 
fered most, while on the third floor the north end (walls and ceiling) was shaken the hard- 
est. In the 6-story, steel frame, brick sugar mill (plate 1174, B) the bricks along the 
I-beams of the north end were thrown out, as were also those of the upper central part of 
the west wall, and part of the top cornices of the north and south ends. Oil in a large 
tank was thrown toward the southeast. The front (north end) of the 2-story brick 
office building exhibits a remarkably symmetrical set of cracks. 

(A. C. Lawson.)—The flood plain of the Salinas River was caused to lurch toward the 
stream from both sides, but the effects are most marked on the south side. The result 
in most places has been the breaking up of the alluvium into monoclinal strips with 
a vertical scarp on one side, facing the river, and a gentle slope on the other. These 
have the effect of landslide searps and terraces, but occur on flat land. In some instances 
it would appear that the ground had collapsed into the cavity formed by the lurching. 
There are minor cracks and buckles in the sand and mud flats of the river-bottom. Here 
numerous craterlets were formed by the sudden ejection of water from the underlying 
sands, due to the compressive action of the shock. This acute deformation of the ground 
accentuated the destructive tendency due to the earthquake shock. 

At the bridge, a large trussed structure in 2 spans having a bearing of N. 27° E., the 
south pier, consisting of 26 piles incased in planking, was thrust to the south between 
6 and 7 feet, so that the entire pier was inclined as shown in plate 123a. The piles were 
not broken at the ground level. The north and middle piers were apparently not 
affected. An oil pipe which crost the bridge was buckled and twisted at the south end 
of the bridge, and when this was repaired the pipe was found to have been shortened 
7 feet. The pipe line extends from the San Joaquin Valley to the Bay of Monterey. 
A few hundred yards to the south of the bridge is a pumping station, and at this point 
some of the connections of the pipes were broken and displaced. The direction of the 
shortening of the bridge span and the pipe is roughly normal to the direction of the San 
Andreas Rift, on the other side of the Gavilan Range. Mr. $8. A. Guiberson, superin- 
tendent of the line, reports that the pipe was broken in about twenty places in the vicin- 
ity of the river, and that at some of these breaks the pipe was pulled apart. 

A few hundred yards east of the bridge, on the south side of the Salinas River, is the 
Spreckels sugar-mill, a steel structure incased in brick, about 500 feet long and about 
150 feet wide, having a northeasterly and southwesterly orientation. This building 
is five stories high, but the five stories occur only at the two ends of the building. In 


116 


PLATE 


A. Near Watsonville. Concrete pier of bridge shattered. Per J.C. 


C. Salinas. Walls of building thrown out. G. R. B. 


io) 








B. Salinas. Wreck of store. G. BR. B. 





D. Moss Landing. Wreck of wooden warehouse. G. R. B. 


ILIAD 'S 3 


, 
i 
Es ‘ 
. 
* 
? 
Ms 
i 
' ° 
+e 
<4 an 
or 
wr. ‘ " 


nt Rs ced eel ey 





PEALE Wh 





B. Spreckels sugar mill. Looking northwest. A. 0. L. 





ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 297 


the middle 100 feet of its length there is only one floor above the ground-level, and above 
this the structure is open to the roof, without cross-ties or floor-beams. ‘This building 
yielded to the shock in a most remarkable and instructive manner. The whole structure 
was shortened along the line of its longer axis, this shortening being effected by the 
buckling of the walls at the middle or weak portion of the building. Both walls bulged 
toward the west, the east wall in and the west wall out, as shown in plate 117, B. 
Within the building considerable damage was done to the heavy machinery, tanks, etc. 
The ground to the south had been much heaved and otherwise deformed, causing the 
wrecking of trestles, pumping-house, and other structures. The rails of a track at the 
rear of the building were pulled apart, due probably to the slumping of the ground 
toward an old slough of the river. 

In the bottom of this slough water gushed forth at numerous places at the time of the 
earthquake. It is said by those who witnessed the phenomenon that the water spurted 
repeatedly as high as 20 feet, and that the outflow of water lasted for 10 minutes after 
the shock. The places where the water spurted forth are marked by areas of fine, light, 
bluish-gray sand, which is said to be known only at a depth of 80 feet in the various 
well borings of the vicinity. In these areas of fine bluish sand are often funnel-shaped 
depressions or craterlets from which the water issued. 

(S. A. Guiberson, Jr.) —As superintendent of the pipe line, I am in a position to say 
that we have no breaks whatever in any place between Coalinga and the Salinas River, 
and there were no fissures of any kind along the line between these points. This I know 
positively, as I have line riders who were instructed to look closely for any disturbance 
of this nature. The line of fissures seems to have ended north of Priest Valley. The 
conditions prevailing along the Salinas River, and some of the peculiar circumstances 
attending the breaking of our line in about twenty places, are of interest. I was on the 
ground the following day, and only regret that I did not have time to have some of the 
peculiar features photographed. In places our line had been broken and the ends were 
3 feet apart; at the same time the ends of the pipe would be hammered up, showing 
that there had been an opening and closing movement at that point, while at other 
points the line would overlap as much as 4 feet. One of our stations is in this zone of 
disturbance, and the engineers, being on duty, had an excellent opportunity to see what 
most of us who were in bed merely felt. They state that these fissures were opening 
and closing, and that the water and sand would go 20 feet in the air as they closed. 

Southward from Salinas (G. A. Waring). — At points along the railroad liquids were 
generally spilt, furniture was moved, and chimneys cracked. At Chualar, 3 out of 29 
chimneys fell, but 2 were on an old house and were probably weak. At Gonzales the 
intensity seems to have been about the same as at Chualar. Out of 150 chimneys 11 
fell, while many were cracked. East of Gonzales, near the foot-hills, houses were barely 
shaken; while to the west, near the river, water-tanks were thrown down. At Soledad 
3 out of 8 chimneys fell, but the number is probably too small to be taken as a criterion 
of intensity. Some plastering on the first floor of the hotel was slightly cracked, a few 
glasses were thrown from the bar, and some of the bottles were turned around. The 
frame of the railroad tank was so badly twisted that it had to be taken down. A chande- 
lier swung northeast-southwest with a double amplitude of 18 inches. 

At King City, close to the river and on low ground, the intensity was considerably 
higher than at Soledad. Heavy objects, such as a printing-press, slot machines, and 
ice-chests, were shifted a little, and a few things were thrown from-the shelves. One 
low chimney on a low fire-wall fell, but the wall was without a crack. No other chimneys 
were injured. The river-bed sank nearly 6 feet in the vicinity of King City. At San 
Lucas the intensity was considerably lower; milk and water were spilt and shelf goods 
disturbed, but no chimneys fell. 


298 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 

On the western side of the valley from Salinas to San Lucas the same kind of evidence 
was found as at corresponding points on the eastern side. At Fort Romie most of the 
clocks stopt, a few articles were thrown from the store shelves, and water in a north and 
south canal was thrown over the sides. No sound was heard during the shake, but it is 
reported to have come afterward. 

About 4 miles south of Fort Romie, water was thrown 30 feet northward from a full 
tank, the top of which is 14 feet above the ground, and half the milk was thrown from 
half-filled pans. West of San Lucas, waves were reported to have been seen moving 
southward over the hills and a sound to have been heard. The shock began gently, 
was followed by a harder shake, and died away slowly. Thru San Ardo, Bradley, 
and San Miguel, the shock lessened uniformly. At San Ardo a water-tank frame was 
somewhat wrenched, and the river-bed is thought to have sunk about 2.5 feet, tho 
evidence of this was not obtained. Oil was spilt from a large tank, and quicksand was 
thrown up in a well, which seemed to lessen the flow considerably. The railway station 
at Bradley, standing on made ground, settled 2 inches at one end. 

At Paso Robles a number of clocks were stopt, most of which were facing east or west. 
Window weights rattled and lamps swung about, but plastering and shelf goods were 
not affected. The duration of the shock was estimated at 40 seconds, but was very 
gentle. 

In the southeastern end of the Salinas River drainage area, at Shandon, Cholame, and 
Parkfield, the shock was notable as being “the longest, easiest one felt in many years” ; 
liquid surfaces were somewhat disturbed, a few clocks were stopt, and hanging objects 
were set in motion. In the hills 2 miles northwest of Shandon the intensity was some- 
what greater, as it was also to the southeast in the Red Hills. At Shandon, a saddle 
hanging by a wire from the rafters swung north and south, and water was thrown from 
a full horse-trough. The shock was also reported at Estrella and Linne. 

South and West of Salinas Valley (G. A. Waring). — Following southward over the 
divide thru Templeton, Santa Margarita, Dove, and Guesta the shock lessened until 
it was hardly more than distinctly felt. At Templeton’ skimmed milk was spilt at one 
place, but unskimmed milk was not. At Dove the swaying of the telegraph wires was 
about the only evidence noticed. At one place a mile east of San Luis Obispo a great 
roar is reported to have been heard. 

In the coastal range of hills thru Carmel P.O., Jamesburgh, and Jolon, only milk and 
water were disturbed, but from the latter place to Los Osos Valley, west of San Luis 
Obispo, the shock varied considerably. At Lockwood the shock was a little stronger 
than at Jolon, clocks being stopt generally and milk and water spilt, but no shelf goods 
were moved. Thru Hames and Pleyto it hardly more than wakened sleepers, and people 
moving around did not feel it; while at Adelaide clocks were stopt, shelf goods moved, 
and liquids spilt. Several minor shocks have also been felt at Adelaide. In Los Osos 
Valley, however, the shock was barely felt; sound sleepers were not awakened. A few 
light things, such as table covers, swayed slightly, but no sound was heard, and pans 
of milk were undisturbed. 

At San Luis Obispo the shock was hard enough to waken all ordinary sleepers. Some 
people thought it a wind-storm. The vibration is estimated by some to have lasted 20 
seconds. Mr. John R. Williams states that the shock made doors and windows rattle, 
moved his bed, and stopt some clocks. There was but one principal disturbance, which 
gradually increased in intensity and then died away, lasting about 50 seconds. The 
apparent direction of movement was northeast and southwest. The night operator at 
the telephone office was talking with Salinas at the time the shock occurred. She heard 
a scream at the Salinas end, followed by a roaring sound. Fully half a minute later the 
shock was felt by her at San Luis Obispo. 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 299 


Along the coast northward from Port Harford thru Morro, Cayucas, and Cambria, to 
San Simeon, the intensity gradually rose. At Morro some people in bed and awake 
felt it; many others did not ;. while at San Simeon liquids were somewhat disturbed and 
the shock of the afternoon (of April 18) was also noticed, which was not the case farther 
south. At Piedras Blancas Light-house a clock stopt and the shock was distinctly felt. 

Between San Simeon and Posts the country is almost uninhabited, and not easily 
accessible, so it was not visited. At Posts a clock was stopt. The shock was very appre- 
ciable, and several minor ones have been felt since. At Idlewild several articles were 
thrown from shelves, windows rattled, and the redwoods swayed considerably. At Sur 
a clock was stopt and the shock was apparently a little stronger. At Carmel-by-the-Sea, 
on deep, sandy soil, several people ran out of doors, a cobble-stone chimney fell, and a 
few tall articles were tipt from shelves. 


SAN LUIS OBISPO TO SAN BERNARDINO. 


This portion of the state is on the southern fringe of the region within which the shock 
appealed to the senses. The shock was not exceptional in intensity and the people paid 
little attention to it; therefore records of observations as to the effects produced are few. 
Such reports as have come in, however, indicate that the shock was more or less distinctly 
felt thruout the country north of the Santa Barbara Channel and the Valley of Southern 
California, as far east as San Bernardino. 

Arroyo Grande, San Luis Obispo County (G. P. Ide). — Pendulum clocks facing north 
and south were stopt, while those facing east and west were not. Very few objects were 
overthrown. A hanging object swung east and west in an elliptical orbit. 

Other points south of the town of San Luis Obispo at which the shock was reported 
are: 

Pismo: Hanging objects swung from east to west, and some clocks stopt. 

Edna and Oceano: Clock stopt. 

Port Harford: Slight shock. 

Santa Maria, Santa Barbara County (F. R. Schank). —I was asleep in the second story 
of a brick building and was awakened by the first of 3 shocks. The shock awoke people 
generally and was observed by persons moving about, but did no damage. The motion 
was a slow, easy one. Wooden inside shutters at my windows swung thru a considerable 
arc, and an incandescent lamp suspended by about 5 feet of cord vibrated with an am- 
plitude of about 6 or 7 inches in a plane approximately east-northeast. The length of 
the first and second shocks was 1 or 2 seconds, but the third shock lasted between 12 
and 15 seconds. 

Casmalia, Santa Barbara County (C. H. Stephens). —I was awakened by the jar, 
and the rocking was continued for about a minute, when all became quiet. It then 
started again lightly, getting stronger as it proceeded and gradually dying away in about 
45 seconds. The third shock came quite strong, and 6 waves followed close on each 
other, each stronger than the preceding one. The clock was stopt, and some articles of 
furniture were overturned. 

Surf. — A clock was stopt. 

Lompoc, Santa Barbara County (C. K. Studley). —I was in bed, awakened by the first 
slight trembling. My bed stands east and west, with the head to the west. The first 
shock moved me up and down from head to foot. The second shock rolled me from side 
to side. The first shock gradually increased to a maximum, and then died out; the 
second seemed to be about the same intensity thruout, and stopt suddenly. The latter 
set the window weights on the south side of the house rattling quite rapidly. The hang- 
ing lamp suspended from the ceiling of the lower story by a chain, which would make 
it about equal to a pendulum that beats seconds, swung in an elliptical orbit, the longer 


300 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


diameter being 10 inches in a west-northwest direction and the shorter diameter 4 inches 
in a north-northeast direction. The motion in the ellipse was clockwise. The clock stopt. 

Point Conception Light-house Station (Mr. Austin). — While cleaning up in the tower 
at 5° 20" a.m., the keeper felt the lens shake. No one else at the station felt the shock. 

Santa Barbara (J. A. Dodge). —I was aroused from a half-sleeping condition by a 
singular rustling noise in the house. None of us recognized it as an earthquake at the 
time. My bed was not perceptibly shaken. Nothing was shaken out of place, no plaster- 
ing was cracked, and no clocks were affected. The sound referred to was produced by 
something in the structure of the house creaking or vibrating. Other reports state that 
some hanging objects were caused to swing, and that one woman was made dizzy. 

Carpenteria, Santa Barbara County. — The shock was sufficient to rattle dishes and 
slightly move beds, but few people were awakened by it. 

Saticoy, Ventura County (Ki. O. Tucker). — Water in a trough which was 6 inches from 
being full, slopt over nearly a pailful at a time from the ends. The trough lies from north- 
east to southwest. A rattling noise was heard in the house, but no motion was felt. 

Hueneme Light-house Station, Ventura County (C. F. Allen). —'The earthquake was 
one abrupt shake which gradually died out, lasting 4 seconds in all. The weight to the 
clockwork which turns the light thumped back and forth in the weight-well from north- 
west to southeast, and the window weights did likewise. 

In Ventura County a slight shock was reported at Newberry Park,.Punta Gorda, and - 
Ventura. At the latter place, hanging objects were observed to sway from east to west. 

Calabassas (H. H. Wheeler). — A farmer stated that a number of cisterns for collecting 
rain-water for domestic uses were cracked by the earthquake shock so that they leaked. 

Santa Monica, Los Angeles County (T. H. Moody). — A disturbance was noticed which 
seemed to be on the front porch, the noise continuing with:considerable regularity, and 
appearing to change from place to place. Then there was other cracking around the 
house, and finally all was quiet. Nothing moved out of place. 

Los Angeles (J. D. Hooker). — There was a light shock, then a heavier; then a smart 
shock which caused windows and doors to rattle. A window curtain swung in and out. 
A brass ring attached to a cord 15 inches long swung northwest and southeast. At the 
Weather Bureau station the barometers were observed to swing and rattle against the rings 
which confined them. The shock was also reported as a slight one at Azusa, Claremont, 
and Toluca, in Los Angeles County. : 

Anaheim, Orange County (J. F. Walker). — Very few people in Anaheim report having 
felt a shock at all. It was very slight. No clocks were stopt. 

San Bernardino (Dr. A. K. Johnson), — The shock was sufficient to stop the town 
clock at 5" 17", and several: persons felt the vibrations, but no movable objects were 
displaced. At 4" 30" p.m., April 18, a slight oscillation was felt which caused the chande- 
lier to sway. This movement continued for a few seconds, and seemed to be from north- 
west to southeast. 


BAY OF SAN FRANCISCO TO THE SAN JOAQUIN VALLEY. 


In Contra Costa and Alameda Counties the destructive effects of the earthquake were 
most manifest in the cities of Berkeley, Oakland, and Alameda, on the east side of the 
Bay of San Francisco. 

Berkeley (A. C. Lawson). — A large majority of the brick chimneys were broken or 
overthrown, and in addition to this several brick buildings had their upper walls thrown 
down or were otherwise damaged by cracks. The most notable cases of this kind of | 
damage indicative of the intensity of the shock may be briefly mentioned. 

At the State Institution for the Deaf, Dumb, and Blind the upper part of the northwest 
tower of the building, to the north of the central structure, was wrecked by a considerable 


PLATE 1/8 





A. Berkeley. Institute for Deaf, Dumb, and Blind. South wing, A.C. L, 


‘ 


res We 





B. Berkeley, Institute for Deaf, Dumb, and Blind. North wing, A.C. L, 


: 
i 
; 
‘ 
be al 
‘ of} 
‘ 
' 
4 ‘ul ‘ 3 
rls Vi 
+ 
* 
: 
ry 
> 
'' 
a) 
\ 7 f . 
4 ~ 5. 
t 
Pa “/ 1, bom ae ». 
Pe ok t., 





PLATE {19 








A. Berkeley. Barker Block. Shattuck Avenue and Dwight Way. A. 0. L, 





B, Berkeley. High-school. A.C. L. 





s 
i 
' 
c i? : 4 
i 
,* 
> <a 
>) a 
: ; Z Myre i eit 
, - é 7 : f 
7) 7 , ; as ’ et gr 
* | 
‘ ‘ ‘ r 





ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 301 


part of the brickwork being thrown out on the northeast and northwest corners of the 
tower. (Plate 118s.) The upper part of a brick gable in the central building, facing 
northerly, was thrown southerly, or into the building. The upper part of the tower 
on the northwest corner of the building to the south of the central structure was de- 
molished. (Plate 1184.) The main clock tower of the Institution, however, suffered 
no serious damage. The clock, a very unreliable one, stopt at about 5" 13". At the 
High School the walls of the upper story, particularly those facing west, were badly 
cracked and partly thrown out, so that they had to be taken down. Two large brick 
chimneys on the east roof collapsed and did much damage to the rooms below. (Plate 
119z.) 

The Barker Block, at the northwest corner of Shattuck Avenue and Dwight Way, a 
building veneered in part with brick, had a great deal of the brick facing of the upper 
part of the building, and much of a strip of tiling above the east wall, thrown down. 
(Plate 1194.) The upper part of the rear wall of the brick building at the northeast 
corner of the same streets was thrown down. The north wall of the new Masonic Temple, 
which was in course of construction at the corner of Shattuck Avenue and Bancroft 
Way, was thrown to the north and caused the collapse of certain steel girders resting 
upon it. 

The intensity of the earthquake within the city of Berkeley was by no means uniform. 
There were areas which seemed to a very considerable extent to be immune to the de- 
struction so marked in the throw of chimneys, etc., in neighboring areas. The buildings 
on the University campus, for example, sustained no serious damage, and there was not a 
single chimney thrown, altho one or two were cracked. In a belt of the city extending 
northwesterly from the vicinity of the President’s residence on the campus, the damage 
to chimneys was similarly light. This comparative immunity to destructive shock 
appears to be associated with the fact that the buildings on the campus, and in the belt 
to the northwest of it, are practically founded on rock, whereas the portion of the city 
where chimneys generally fell is on alluvium. 

The direction of the fall of chimneys at Berkeley, as elsewhere, was controlled to a large 
extent by the orientation of the houses. Chimneys usually fell nearly at right angles 
to the longer side of their cross-section, which was as a rule parallel to one of the walls 
of the house. Notwithstanding this fact, however, there was a prevailing tendency in 
the fall of chimneys to the south and east, or in the southeast quadrant. Where chim- 
neys fell to the east, they fell usually a little to the south of the line at right angles to 
the north and south wall; and where they fell south they fell similarly a little to the 
east of the normal to the east and west wall. Some square chimneys fell diagonally 
to the southeast. This was true of a rather massive 4-flue chimney on the writer’s 
house, which fell at the latter end of the shock. In many cases chimneys were 
dislocated and twisted, without being thrown down. Of 38 chimneys, the rotation of 
which was noted by observers giving their entire attention to the matter for the time 
being, 31 were rotated counter-clockwise and 7 were rotated clockwise. In some parts 
of Berkeley the rocking of the houses was sufficiently violent to make it difficult, and in 
some cases almost impossible, to stand on the floor without support. 

According to the observations of the writer, there were two maxima in the shock, with 
a lull in the interval, the second being the more violent. The movement appeared to be 
diagonal to the rectangle of his house, the longer side of which is approximately east and 
west. The throw of objects was much more to the west than to the east. This was well 
exemplified by the behavior of objects in the mineralogical museum on the third floor 
of South Hall. These are upright cases reposing on cabinets of drawers. The shelves, 
arranged in steps, are orientated north and south approximately, and face both east and 
west. On the shelves facing east very little was disturbed, while in those facing west 


302 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


many of the heavier specimens, weighing 20 pounds or more, were projected from the 
largest, or top shelf, thru the glass doors, and were found strewn on the floor. In no case, 
however, was the glass of the doors broken. ‘The latter had been forced open at the same 
moment that the masses of rock had been hurled toward them, thus allowing the missiles 
to pass thru. Smaller specimens, weighing less than a pound, on the shelves imme- 
diately below the top one, were very little disturbed. 

Oakland (A. C. Lawson). — The destructive effects of the earthquake were much more 
in evidence in Oakland than in Berkeley, and this is doubtless due in large measure to the 
much greater number of brick and masonry structures susceptible to this kind of damage. 
When particular instances are considered, however, it seems probable that the severity of 
the shock was in reality somewhat greater in Oakland than in Berkeley. Chimneys fell 
very generally thruout the city; the upper parts of brick walls, gables, and cornices 
were in many cases thrown down (plate 1228) and cracks in walls were numerous. The 
underpinning of some few old frame houses caused these structures to collapse. In 
addition to this damage, which indicates fairly well the prevailing intensity of the shock, 
there were several cases of more severe destruction which must be noted. 

The Prescott school, in course of erection, at the corner of Ninth and Campbell Streets, 
was rather badly wrecked (plate 1218), as was also the building of the California Flax 
Works, on the corner of Union and Third Streets, the walls of which gave way, causing 
the roof to collapse. (Plate 1214.) The susceptibility of this building to destruction 
was probably due to lack of transverse bracing for the walls, except that supplied by 
the roof girders. The southeast tower of the First Baptist Church, on Telegraph Ave- 
nue, had its upper northeast corner thrown out, and was otherwise wrecked. (Plate 
1224.) The east and south gables were both thrown out; but the lower towers at the 
northeast and southwest corners of the building were comparatively unaffected. The 
Central Bank building, at the corner of Fourteenth Street. and Broadway, had the brick- 
work of its southwest corner thrown off from the 2 upper stories, and was similarly 
affected, tho to a less extent, on its northwest corner. (Plate 120.) The large smoke- 
stack at the Key Route power generating plant, built on the tidal marsh land, had its 
upper third thrown off. (Plate 120s.) 

Considerable damage was also done to the First Unitarian Church, at the corner of 
Castro and Fourteenth Streets, and to the Christian Science Church, at Franklin and 
Seventeenth Streets. 

(E. C. Jones.) —There were very few breaks in cast-iron gas-mains. Two of these 
were caused by impact of heavy débris falling from buildings and poles. One was on 
Washington Street, where heavy blocks of sandstone fell from the third story and the 
roof, breaking the main 30 inches below the bituminous rock. Another was at the corner 
of Fourteenth Street and Broadway, where a transformer fell from a pole, striking the 
center of a short car rail and bending up both ends. A 38-inch cast-iron main a short 
distance from this was broken at right angles. On the Twelfth Street dam, a cast-iron 
pipe was broken and displaced over a foot; while the high pressure steel pipe paralleling 
it was practically undisturbed. Gas-holders were uninjured, tho much of the water 
was thrown out of the holder tanks. The only damage to buildings was the destruction 
of brick gables at Gas Station ‘“‘B,” First and Market Streets. 

Oakland cemeteries (R. Newcomb). — In the Mountain View Cemetery, which is on 
a little draw between ridges, the chief damage done was the cracking of the receiving 
vault, and that was not injured very much. 

In St. Mary’s Cemetery, on the small ridge to the west, however, many monuments 
were moved or twisted and several were overthrown. On entering the cemetery from 
the east, very little damage was observed, but on climbing the ridge more and more was 
noticed. On the north slope less damage was done, and on level ground farther north 


120 


PLATE 





Oakland. Central Bank Building, G. K. G. 





B. Oakland. Smokestack of power plant, Oakland Traction Company. A. 8. E. 





. 
‘ 
< y s 
. RY 9 SS 
ig eating wee = coy nese er sr eineea ase maar spe ear le cw Fe es 
a ae é ae 
: cy uy Pay } et 
Wane gh to = - 
ems al 
. a NR 
ba ij 
+ @ in} Ve ae oe 
e A 
. ; " ' i ale ‘ 
i f 7 : 
ts +* 
F Tr 
> Ue 
-! -! 
+ 
a, 
. 
? 
e 
» : 
. 
. 
Pa 
’ 
' 
i 
f 
7 . 
7 
' 
2 
ee ee ot ee ee ee 
. 
6 
° 
> 
¥ 
~ call 
a 
2 
f 
vat 
. 
, 
4 
‘ 
3 
i 9 
. a 
’ 
% , 
[ by 
ve 
¥ , ay . 
aly i" 
mes 





PLATE 121 





A, Oakland. Flax works, Union and Third Streets. A. 8. E. 


Pie. 


SEP ERT Me emacs: 





B. Oakland, Prescott School, Ninth and Campbell Streets. A. 8S. E, 





122 


PERE 


A. Oakland. First Baptist Church, Telegraph Avenue. G. K. G. 


. 
2 


Che Sane 





=P omens 


_ 


eT elas 





B. Oakland. Fourteenth Street, between Washington and Broadway. 


had 







ra oh = 
VE ae : Ls ¢ 
of ehh oS Se 


pine AOR a ce tee ‘ 





i Be 
My Fe ON Ae fe en 
> k S te 
s , = s 
3 » Li ‘ Lane ~ 


¥ .f —_ 
» 
irs At 
a Pam * 
$4646. 
‘ 
> 
é 
. al 








i. » 
4 a 
7 = 
‘ 
ral 
ay: ee 
+ - sm 
" 9 
ova i>. 
F ve 
: ‘ ; 
vs 
y ’ 
F ‘ 
. 
~— 
. i4 
. a ; me 
a “Te: R 
+ f FR wae ; 
POR Dat ges: a 


é _ det ~ 
eo rmreens ein art Nerang ee Sasa ha aes eT A oeina sies =s 


22 eR ee ea ee emcee nat arg atone rye 


tke PM 8 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 303 


absolutely no monuments were affected. Near the top of the ridge many monuments 
were overturned, and nearly all of them showed twisting or shifting. The result of the 
shock upon the monuments in this cemetery may be summarily stated as follows: 

Fifteen were rotated counter-clockwise, 4 of these thru from 1° to 2°; 6 thru 5°; 1 
thru 15°; 3 thru from 5° to 8° with a lateral shift of 1 inch to the east; and 1 thru 8° 
with a lateral shift to the south. 

Six were rotated clockwise, 2 of them thru 25° to 30°; 1 thru 15°; 1 thru 10° with a 
lateral shift of 6 inches to the south; and 2 thru 2° with a shift to the south of 1 inch. 

Six fell to the east, 1 to the west, and 1 to the north. 

Three were shifted laterally from 0.5 to 1 inch to the east, one 1 inch to the south- 
west, and one 1 inch to the south. 

(B. McGregor.) —Of 12 monuments in Mountain View Cemetery that were disturbed 
by the earthquake, 10 are rectangular shafts which were simply twisted on their bases, 
4 from left to right and 6 from right to left. The other 2 are turned shafts, both of 
which slid on their bases about 2 inches south. There were a few others displaced. 

Alameda. — The destruction was confined for the most part to the throw of chimneys 
and the upper portions of brick walls. A few tanks were also overthrown, and 3 large 
stacks near Pacific Avenue and Lina Street. Messrs. Pond and McFarland counted 
619 fallen chimneys in the city; of these they report that 189 fell to the southwest, 143 
to the southeast, 93 to the northwest, 97 to the northeast, 34 to the south, 14 to the north, 
25 to the east, and 24 to the west. 

The fall of chimneys was evidently determined largely by the orientation of the houses, 
which have their walls in nearly all cases orientated at right angles to the direction given 
for the fall. The statistics are quoted not because they have any special significance, 
but because they indicate how little this class of phenomena contributes to the elucida- 
tion of the character of the earth movement, unless each particular case is studied in all 
its bearings. 

With regard to the chimneys which were dislocated and twisted, there appears to 
be more constancy of result. The same gentlemen counted 61 such chimneys and of 
these 58 were rotated counter-clockwise and 3 clockwise. 

Southeast of Oakland (G. Backus and R. P. O. Newcomb). — In the vicinity of High 
Street about half of the chimneys fell. The most general direction of the fall was to 
the north and south, altho some fell east and west when the slope of the roof was in that 
direction. Plastering in the houses was severely cracked, but no foundations nor build- 
ings were damaged to any visible extent. A large smelter chimney in the vicinity was 
not damaged by the shock. 

At Fitchburg about the same state of damage was seen. The chimneys on the old 
houses were gone. A large school-house with a brick foundation was not injured. 

At Elmhurst the windows in the hotels and stores were broken. Most of the chimneys 
had fallen, one in particular being thrown to the east against the slope of the roof. 

At San Leandro half the windows in the stores were broken, and nearly every chimney 
was down. All loose objects in the houses, such as dishes, ete., were thrown down. 
The plastering was greatly cracked. The houses were not seriously damaged, and only 
2 have been condemned. 

At Junction City the shock was about the same as at San Leandro. According to 
rumor a 3-inch fissure opened up between Junction and San Lorenzo, but this was not 
seen. 

The County Hospital, but a short distance from the Junction, was only slightly dam- 
aged. None of the chimneys were thrown over and plastering was not cracked. The 
Hospital is built on solid ground, and several quarries can be seen in the ground upon 
which the buildings are situated. 


304 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


At the San Lorenzo Cemetery, about half the tall monuments were down. Most of 
these fell to the south, some to the north, and a few to the east and west. Twisting 
occurs where the south end is thrown east. Almost all the chimneys in this vicinity 
were down. 

At Mills College about half the chimneys were down. A stone building there was 
badly shattered and will have to be taken down. A brick and concrete library, and the 
same kind of a bell-tower, were not injured to any great extent, tho a few cracks can 
be seen here and there. Mills is on rather high ground at the base of the foot-hills. 

(J. Keep.)—The floor of my room at Mills College seemed to be boiling. Immense 
damage was done. In the made ground there was a drop of from 1 foot to several feet. 
The seismograph registered for a time and then broke. The Science Hall, a stone struc- 
ture, was badly injured, entailing a loss of $5,000. 

(J. N. Frank.)—In San Leandro objects against the east and west walls of the house 
were thrown down. Some statues were rotated clockwise. Chimneys were overthrown 
or broken, and plaster cracked, causing a damage estimated at between $400 and $500. 

Mount Eden (William Gall). — The general direction of the movement was to the 
north and northeast, but objects fell in all directions. Objects were rotated, some 
clockwise and some counter-clockwise. A rotary motion was distinctly felt. Brick chim- 
neys were broken and thrown. Furniture was thrown flat. The shock caused con- 
sternation among the people and domestic animals. Monuments in the cemetery were 
overthrown in various directions. 

Decoto (¥. i. Matthes).— No earth movements nor displacements were discovered 
anywhere along the base of the mountain scarp. The damage to buildings was slight, 
consisting of broken or twisted chimneys and cracking of plaster in a few houses. A 
few scattering chimneys escaped destruction, being probably better built than the aver- 
age. In the stores and saloons articles were thrown down in southerly directions for 
the most part. Water was observed to splash from a tank a mile north of town, the 
direction of throw being southeasterly. The consensus of opinion was that the shock 
had a nearly north-south direction. According to the track-boss, the railroad track 
suffered no displacements anywhere between Niles and Irvington. The Masonic Home, 
a large brick structure located on the hillside on solid rock foundations, suffered but 
little damage. A few insignificant cracks in the brick walls, 2 chimneys broken off, and 
2 chimneys cracked constitute the most serious damage. Plaster was cracked in several 
rooms; no windows were broken. / 

Alvarado (F. KE. Matthes).— The Alameda Sugar Company was the chief sufferer. 
The main buildings of the plant are of wood, substantially constructed, and were not 
damaged; but the fittings and accessory structures were injured in numerous places. 
An old lime-kiln showed diagonal cracks in the brickwork; several of the small arches 
above the fire holes opened and let bricks fall out. A 6-inch cast-iron water-pipe, at- 
tached vertically to the main building, broke transversely about 30 feet above the ground. 
The water in the tanks on the roof splashed so heavily as to raise and break the wooden 
covers. The water seems to have splashed mostly to the east. The 2 great platforms 
carrying the molasses tanks, supported by numerous vertical props 10 feet 10 inches 
high, resting on concrete foundations, fell down altogether; the northern one to the 
north, the southern one to the south, these directions probably being determined by 
the original inclination of the supports or the relative efficiency of the bracing. The 
tanks were all damaged and over 1,000,000 pounds of molasses flowed away. The total 
weight on the south platform was 1,072,891 pounds. (Plate 1154.) In the engine-room 
the vertical steam-pipes cracked next to the flanges by the wracking motion of the ceil- 
ings thru which they extended. The shock appears to have had a north-south direction, 
according to the position of the breaks in these pipes. 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 305 


The mill stands on flat, alluvial ground 100 feet north of Alameda Creek. Along 
the banks of the latter a large number of cracks extend, roughly parallel with the stream. 
Considerable masses next to the stream-bed slumped toward the same, leaving gaping 
cracks 1 to 2 feet wide, and carrying with them small outlying buildings, notably the 
fire-engine house, which moved bodily, concrete foundation and all, 2 feet south toward 
the creek. A small railroad trestle southwest of the mill moved 4 inches south on both 
of its abutments, probably owing to slumping of loose ground on the north side of the 
creek. A 2-inch water-pipe, laid under the ground some 60 feet north of the creck and 
almost parallel with the same, shows indications of having been submitted first to ten- 
sion, causing rupture at one of the joints, then to sudden compression, causing it to be 
jammed together with violence. 

Cracks in the ground may be found as far as 250 feet from the creek. They were 
nearly all closed at the time of the visit (May 7), but were easily traced by the streaks 
of bluish-gray sand which has issued from them, together with considerable quantities 
of water. According to the Chinese cook of the superintendent, the cracks nearest to 
his dwelling opened and closed several times in succession during the quake; and large 
volumes of mud-laden water gushed from them, splashing up some 10 feet in the air at 
each closing. A large crack of this kind opened under the northwest corner of the dwell- 
ing, and the superintendent estimates that fully 500 gallons of water gushed from it, 
the flow continuing with decreasing volume for about an hour. The fence in front of 
the house shows that the ground there has been raised into a low hump. The sewer 
pipe leading west to the creek was detached from the house by a space of 22 inches. A 
chimney near the northeast corner of the house was thrown to the east with sufficient 
violence to throw the farthest bricks 35 feet east of the house. The top of the chimney 
was only 20 feet above the ground originally. 

In the roadway south of the mill, water oozed out in a number of places, without the 
production of visible cracks. The water pipes and hydrants in this vicinity were crusht 
in several places. 

At the Alvarado Water Works the brick buildings suffered considerable damage, the 
walls cracking in several places. Nothing could be learned regarding the behavior of 
the wells of this plant. The frame dwelling of the superintendent was damaged by the 
collapse of its underpinning. A similar fate befell the Alvarado Hotel. Both houses 
were being put in place at the date of the visit. At the school-house the water-tank fell 
owing to the collapse of its supports. 

Nearly all brick chimneys in the village fell, the directions varying. A few cracks 
opened across the streets, but these had been filled on the date of the visit. The con- 
sensus of opinion was that the shock had a north-south direction. 

Lick Observatory, Mount Hamilton. — From the reports of astronomers C. D. Perrine, 
R. G. Aitken, H. K. Palmer, K. Burns, A. M. Hobe, and G. A. Vogt the following obser- 
vations as to the character and intensity of the shock have been obtained. The prin- 
cipal disturbance was preceded by a tremulous motion variously estimated at from 
11 to 15 or 20 seconds. There seemed to be 2 maxima, the first being the stronger (?), 
according to H. K. P. There was a first secondary maximum about 5 seconds after the 
beginning, a maximum 11 seconds after the beginning, and another secondary maximum 
about 15 or 20 seconds after the beginning, according to K. B. 

A tremulous motion was felt after the principal disturbance. 

“Heavy vibrations were still felt 60 seconds after the first count. Motion was felt for 
nearly 2 minutes after the first count.” C.D.P. “The duration of this tremulous motion 
was about 30 seconds. Vibrations stopt in the house at the end of that time.’ K. B. 

“Duration between 30 and 35 seconds.” A. M. H. 

No vertical motion was perceived, nor was any recorded on the Ewing seismograph. 

x 


306 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


According to C. D. P., the heaviest movement seemed to be nearly east and west ; 
while according to K. BL it was northwest and southeast. On the Ewing seismogram, 
the north and south component seems to be the most violent, the pen having left the 
plate for half a revolution of the plate. The east and west vibration was extremely 
large. The maximum of the east and west movement occurred after the pen of the 
north and south component left the plate. 

A razor strop hanging on a north wall, the only thing free to swing, swung east and 
west about a foot (double amplitude). A shaving brush which stood up on end and, 
being round, could fall in any direction, fell west. Things overturned fell east and west. 

Ak He shoe k was severe enough to make windows rattle and doors swing. Book-cases 
were moved out about an inch from east and west walls, but not from north and south 
walls. A pendulum clock on a north wall stopt at 5° 1" 52". Not much plaster fell, 
and only 1 of a dozen or more chimneys was thrown. Some other chimneys, principally 
those of a 3-story brick house, were cracked and shifted. 

The earth-waves were very long, but smooth. 

According to K. B., the shock was accompanied by a sound as of the flight of birds. 

The water in Smith Creek on the afternoon of the day of the shock was of a light slate 
color; not yellowish, as after heavy freshets. 

“Standing in the doorway and looking out the east window, I could see the walls of the 
brick house shaking. There seemed to be a great deal of dust in the air in front of the 
window.” H. K. P. 

The movement of the east-west component of the Ewing seismograph indicates an 
intensity corresponding to an acceleration of 400 mm. per sec. per sec. The north and 
south pen left the plate, owing to the violence of the shock. 

Niles (R. Crandall). — The town of Niles stands on gravels of the alhrvidl fan at the 
mouth of the Niles Canyon, and is about 20 miles due east of the fault at its nearest point. 
At Niles there were no large buildings, and most of the structures were not strong, but 
there was no serious damage done to any of them. About 56 per cent of the houses had 
either terra-cotta chimneys or tin pipes, which are much harder to shake down than those 
of brick. Of all the chimneys in town, 48 per cent fell; of the brick chimneys 80 per cent 
fell; of the terra-cotta chimneys only 10 per cent went down. 

Most of the houses were not plastered, so no notes could be obtained on that subject. 
In nearly all of the houses such objects as dishes, bottles, vases, and clocks were thrown 
from the shelves. Milk and water were spilt from open receptacles in most cases. 

A concrete abutment of the bridge across Alameda Creek was cracked. A man out of 
doors at the time found much difficulty in walking. A 50,000-gallon water-tank fell at 
the Niles railway station. Similar tanks were thrown down at the stations at Pleasanton, 
Livermore, and Lathrop. This was due to imperfect construction rather than to the 
violence of the shock. The tanks were upon cast-iron pillars originally, but when new 
and larger locomotives were put into service on the railway, it was found necessary to 
have the water-tanks set higher. This was accomplished by inserting short blocks be- 
tween the tanks and the tops of the pillars. When the weight of 200 tons was swayed 
on this sort of a structure, the tank collapsed. 

While at Niles, a visit was made to one of the new tunnels of the Western Pacific Rail- 
way, which is about 1 mile east of Niles in the Niles Canyon. The tunnel had penetrated 
about 130 feet into the hillside, but had not yet past thru anything but a sandy clay. 
During the previous winter the walls at the portal, and also on the inside, had stood with- 
out timbering. Since the earthquake it had been impossible to break out more than 4 
feet of ground ahead of the timber sets without caving taking place. There had been an 
apparent movement in the soil which had removed its consistency and made it incoherent. 
The amount of water present in the tunnel was perceptibly changed. The foreman said 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 307 


that there was more water since the shock than there had been even in the wettest part of 
the winter. 

Sunol (R. Crandall). — Sunol is a small town in the north end of Sunol Valley. The 
intensity of the earthquake there was of especial interest, because the town lies almost 
upon the line of the Sunol fault. This fault is the largest one known in the Mount 
Hamilton range, and has a northwest-southeast trend parallel to that of the San Andreas 
fault. It was expected that some compensating movement might be found to offset the 
slip along the San Andreas fault, and this Sunol fault was considered the one most likely 
to show that compensatory movement. The town stands partly on gravels and partly 
upon hard sandstone. The gravels are quite firm; much more so than the gravels on 
which the town of Niles is built. The gravels at Sunol are not thick, and the foundation 
is much firmer than that at Niles. It was quite apparent that Sunol had not felt the 
shock as severely as it had been felt at Niles, 6 miles to the west, or at Pleasanton, 6 miles 
farther east. Only a small percentage of the chimneys fell. Of other objects, few except 
bottles and vases fell; and a window was broken at the post-office. As there was no 
movement along the Sunol fault, the intensity at Sunol was less than at Niles, but the 
fact that it was also less than at Pleasanton shows that the difference must be in the 
formations underlying the two towns. 

(IF. EK. Matthes.) —Over 75 per cent of the chimneys in Sunol were broken. Some were 
twisted in a clockwise direction, while others were apparently thrown straight, most 
of them to the east. Many chimneys were cracked but were still in place. A few win- 
dows were broken, notably those of the post-office. The town is on alluvial ground, 
close to the hills. The depth of alluvium is estimated at the ereek-bed to be about 
50 feet. The steel bridge southeast of the town was found entirely undamaged. The 
flume between Sunol and Niles was damaged at a point 2.5 miles below Sunol. A few 
boards were knocked out of place, but the damage was slight and quickly repaired. 
The Apperson house, a substantially built structure with strong chimneys, had two of 
the chimneys twisted and one left intact. 

Verona (F. EK. Matthes). — All the chimneys on the main house of the Hearst residence, 
6 in number, were cracked, but none was thrown down. The studio has a long crack 
running immediately above the projecting beams supporting the roof, along the northeast 
wall, 18 inches from the eaves. No damage was occasioned to plaster or walls, except in 
the studio. The chimney of the power-plant, at the foot of the hill, was found cracked. 
The “cottage,” built of wood, suffered no damage. No windows were broken. 

Pleasanton (R. Crandall). — The town is on a flat valley-floor composed of gravels, 
apparently the same as those at Sunol, but of a later age. Probably the Sunol gravels 
washt down from the hills to form a valley-floor. The ground upon which the town is 
built, then, is similar to that at Niles. The shock was felt quite sharply at Pleasanton, 
but not so much so as at Niles. Such articles as vases, clocks, and dishes fell in most cases 
and milk and water were spilt from open vessels. Practically no plaster fell, but houses 
that were plastered had numerous cracks in the walls. 

The intensity, as shown by falling chimneys, was as follows: 30 per cent of all 
chimneys fell; 48 per cent of the brick chimneys fell; 30 per cent of the chimneys were 
terra-cotta, but only 3 per cent of these fell; of the brick chimneys which did not fall, 
30 per cent were cracked. 

(F. I. Matthes.)—About 50 per cent of all brick and tile chimneys in Pleasanton were 
thrown down. No marked preponderance in any one direction was noted. Nearly 
every brick building in town was somewhat injured. Cracks in the masonry and the dis- 
lodgment of occasional individual bricks in arches above windows and cornices constitute 
the principal damage. The only stone house, a 2-story saloon, suffered more severely 
than any of the brick buildings, the walls being badly cracked at the corners and even 


308 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


partly thrown down at the northwest corner. Wooden houses suffered no damage except 
the cracking of plaster. No window panes were broken. 

Two bridges near Pleasanton were inspected, one north of the town over Arroyo Valley 
and the other over Arroyo de la Laguna, 1.5 miles west of the town. These bridges rest 
on conerete abutments, and examination showed that in both cases the concrete had 
sheared horizontally by the longitudinal oscillations of the superstructure. The cracks 
were about even with the lower side of the stringers. In the case of the first bridge 
mentioned, these cracks extended to the wing wall at the south end. A vertical crack was 
also found near the west corner of the south abutment, running thru the entire height of 
the structure. A similar crack was also found at the east corner of the north abutment. 
The disposition of these vertical cracks seems to indicate torsional movements of the 
bridge, with right-handed rotation. The concrete was of poor quality, being traversed 
by streaks of coarse gravel alternating with others of finer texture. 

Thru the courtesy of F. H. Tibbets and Harold Woods, surveyors for the Pleasanton 
Hop Company, access was obtained to their records on well borings made in the neigh- 
borhood of Pleasanton. Most of these borings did not reach bedrock, but 2 of them did: 
one near the graveyard south of Pleasanton, which strikes disintegrated shales at a depth 
of 275 feet; the other 0.75 mile northeast of Pleasanton, just south of the railroad track, 
which strikes similar material at a depth of 180 feet. 

Livermore (F. E. Matthes).— Many chimneys were cracked and about 50 per cent 
thrown down. Several tall brick chimneys in various parts of the town were left intact. 
Those on brick piers between Livermore and Pleasanton were undamaged. A block of 
old, weak-looking buildings northeast of the depot suffered no more than a few cracks. 
Glassware in saloons and bars was thrown to the floor in quantities, in various directions. 
A heavy water-tank at the depot fell, owing to weakness of supports. The direction of 
the fall is north, but this is not necessarily indicative of the direction of the shock, as the 
wooden support probably gave way piecemeal. Concrete bridges about town were unhurt. 
The town is on alluvium. 

An interesting feature appears 0.25 mile north of Meyn’s ranch, west of the road leading 
north from Livermore, about 2 miles northof that place. It is on the summit of a smoothly 
rounded hill, sloping gently down to an even, peaty meadow traversed by the arroyo of 
Cayetana Creek. The hill is really one of a number of spurs of the higher land south of 
the meadow. Its soil is peaty, with many sun cracks due to recent drying. Deep cattle 
tracks show that it must be quite soft in wet weather, much like the adjoining meadow. 
The summit of the hill in question was found crowned by a series of concentric deforma- 
tions, rising stepwise above one another. A number of nearly concentric cracks were 
found extending northward into a sort of panhandle, along each of which an upward 
movement of the soil had apparently taken place. The uplift along the 2 principal cracks 
was found to be 19 and 16 inches, respectively. Along the minor cracks the vertical 
displacement amounted to an inch or two only. The surface of each step or bench was 
found to slope inward, and in some places the edge even appeared to have curled inward. 
The material must have been wet and more or less plastic at the time of the disturbance, 
but has since dried and hardened, as peaty soil will in dry weather. While the phenom- 
enon is described by many as a “mud flow” or “mud spring,” there are no indications 
whatever of a “flow,” strictly speaking. The inward slope of the raised benches sug- 
gests the dropping back of the central portions after their upheaval; the scarps remain- 
ing, probably, owing to the friction between the opposite walls of the fissures, which 
prevented the complete return of the adjoining edges to their former level. ‘The concen- 
tric arrangement of the cracks seems to indicate a centralized upward thrust, and the 
small diameter of the entire deformation shows that the effect of the thrust rapidly 
decreased away from the center. While there is no rock visible, it is quite possible 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 309 


that the hill has a sort of rock-core, some distance below the surface. The shock felt 
at Meyn’s ranch was not particularly violent and caused no damage to the buildings. 
(See plate 1414.) 

(R. Crandall.) —Geologically, Livermore is on a floor similar to that of Pleasanton, but 
geographically it is about 6 miles farther east and farther from the San Andreas fault. 
The shock at Livermore was not severe, and but little real damage was done. <A few 
objects of unstable nature fell, and in the larger number of cases milk and water were 
spilt from open vessels, but not in all cases." Most of the houses in town were not 
plastered, but only a few of the plastered houses had the walls cracked, and in only one 
case was plaster known to have fallen. 

An excellent opportunity was afforded to see the effect of the motion upon pendulum 
clocks. In one jewelry store every such clock stopt, regardless of the direction in which 
the pendulum swung. One clock which had not been running before the earthquake, 
was started. Its pendulum swung in a northwest-southeast direction, as in the case of 
several clocks that stopt. About 5 per cent of the brick chimneys fell, with less than 15 
per cent cracked. 

A curious phenomenon was observed near Livermore, the explanation of which is not 
clear. At the Alviso ranch, a little over a mile north of the town, the top of a small hill 
was broken up at the time of the earthquake. The breaking of the ground did not con- 
sist of fissuring along a line, but was in the nature of an uplift of a limited area. There 
were 3 fairly well marked concentric rings where the ground had broken, the inside ring 
in each case being forced higher than the outside ring. The effect was similar to that 
obtained by placing 3 plates of different sizes within each other. The accompanying 
photograph (plate 1414) shows this feature fairly well. It was said by people in the 
vicinity that there was mud in the cracks at the time of the earthquake, but there were no 
evidences of any at the time of the writer’s visit several weeks after the shock.’ 

(Elmer G. Still.) —The Southern Pacific Company’s 20,000-gallon water-tank fell in a 
north-northwest direction; tombstones fell in various directions; a hanging lamp was 
caused to swing counter-clockwise, with the longer diameter of its orbit east and west. 
Mr. Still was asleep and was awakened by the bed being shaken north and south; the 
motion after that was in every direction. Water spilt from full tanks mostly on the east 
and west sides. Mr. Still reports that where the ground was deformed in concentric ridges, 
as described by Mr. Matthes and Mr. Crandall, there was an alkaline spring years ago. 

Santa Rita, 3 miles east of Dublin (F. E. Matthes). — A small, flat levee along the east 
bank of Tassajara Creek, immediately north of the main road, showed several somewhat 
erescentic cracks along which the ground had slipt down and toward the creek from 1 to 
3 inches. These cracks extended farther south, according to local settlers, and crost the 
road; but this was no longer traceable at the time of the visit. Chimneys had fallen on all 
the houses, but as they were not of brick the damage was slight. In the grocery store and 
bar-room articles were thrown in a southerly direction. 

Dublin (F. E. Matthes). — The damage consisted of a few chimneys broken off, and 
articles thrown down from shelves and counters. A water-tank 2 miles east fell from its 
supports, probably owing to the weakness of the latter. Several other tanks in the neigh- 
borhood were injured. 

San Ramon (F. E. Matthes). — Most chimneys had fallen. San Ramon saloon, south 
of the bridge, slid off its foundations in a northerly direction. The west end moved 
3 feet, the east end about 15 inches, being stopt by a fence-post. Several window panes 





1 This may be contrasted with Pleasanton, where at all the houses visited there was only one where 
milk was not spilt. 

2 A somewhat similar phenomenon was seen on Cahill’s ridge in San Mateo County, but there was 
nothing to suggest an explanation. 


310 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


were broken in the building, and glassware was wrecked in quantities. Neither church 
nor school-house suffered any damage. The shock was mostly in a north-south direction. 

Danville (F. EX. Matthes). — Most chimneys were cracked or twisted; a few were 
broken off completely. Glassware in saloons and goods in a grocery store were thrown 
down in quantities in various directions. Water was observed to splash out from two 
tanks in the village, in a southerly direction in each case. Water-pipes laid over the 
surface of the ground at a neighboring ranch were reported to have been thrown out of 
alinement. 

Walnut Creek (F. E. Matthes). — About 50 per cent of all chimneys were thrown 
down. <A water-tank at the livery stable fell. Goods in the grocery store were thrown 
down in quantities. The direction of the shock was not ascertainable. Two barns, 
weak structures, were moved slightly from their foundations. Plaster in several houses 
was cracked. 

Clayton (G. D. Louderback). — At the northern base of Mount Diablo the intensity of 
the shock was much less than in the alluviated valley-bottom at Concord. No chimneys 
were thrown down, and no dishes nor glassware were knocked off shelves, but milk in 
pans was skimmed by the rocking motion. On a hillside above Peach Tree Spring, on 
the west side of Mount Diablo and very near the contact of the Knoxville shales and the 
Franciscan, a crack opened in the ground about 80 feet long, in a north and south 
direction, gaping 4.5 inches. 

Concord (F. EK. Matthes). — Conditions here were much the same as at Walnut Creek. 
The only brick building, a bank, was cracked. Most of the chimneys were cracked, and 
about 50 per cent had fallen. A water-tank at the depot was thrown down. 

Martinez (F. E. Matthes). — Most of the brick buildings here suffered severely ; nearly 
all are more or less cracked, and the stone facing of several was partly demolished. 
The roofs of the bank and other buildings were wrecked. A small stone house, built 
of large blocks, was completely ruined, probably owing to vigorous vibrations of an 
adjoining wooden water-tower near the Alhambra Hotel. The stones started in the east 
abutment of Main Street bridge. Many window-panés were broken. Most of the chim- 
neys were broken off. ‘The court-house was little injured, except for the pediment above 
the entrance, where many large stones have been loosened. One of the chimneys of 
the Bull’s Head Oil Works lost a corner; the others were left undamaged. The railroad 
track east of Martinez, near Bull’s Head Oil Works, was thrown 3 inches out of aline- 
ment to the north. Many cracks occurred in the embankment on both sides of the track. 
A series of 5 small transverse waves was found in the embankment about 0.5 mile west 
of Peyton Station. The distance between crests was about 10 to 15 feet; amplitude 
estimated at 3 inches. This embankment lies in flat marshy land. A small railroad 
bridge near Avon Station was thrown 4 inches toward the east abutment, but it had been 
repaired at the time of the visit. 

(W. Stoddard.)— Buildings were loosened in general, the fronts of some falling out. 
The north and south walls seemed to suffer most. Parts of a large wooden building, 
particularly the window-sashes, were moved in a southwesterly direction. 'The wooden 
props supporting another building were tilted a little toward the southwest. Another 
building was moved 0.5 inch toward the south. The southern part of the town was 
damaged more than the northern part. In the cemetery 6 slabs and pillars fell a little 
east of north; 2 pillars fell to the west; 2 pillars were twisted on their bases and shifted 
to the west; 1 pillar was tilted to the south immediately next one which fell to the east. 
A clock at the court-house had its pendulum broken. The pendulum was about 2 feet 
long. The level of the underground water rose after the shock. 

Cornwall and Black Diamond (E. 8. Larsen). — The towns are about 0.5 mile apart, 
both located on the bay flat and underlain by a tough hardpan. A very few things 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. ole 


were thrown from shelves; one rickety chimney was thrown, and one concrete wall in 
process of construction fell. Less than half the clocks were stopt, though nearly all 
sleepers were awakened. Most of the houses are small and have terra-cotta chimneys. 

Antioch (EK. §. Larsen). — Antioch is on the same sort of ground as Cornwall, but 
there are more brick buildings and more moderate-sized buildings with brick chimneys. 
A few chimneys were twisted on their bases, several were thrown entirely and about 
25 per cent of them needed repairing after the shock. Out of about 12 brick buildings, 
the tower of the Catholic church was somewhat damaged, and one rickety old brick 
building fell. None of the good buildings were damaged. <A couple of windows were 
broken, a few clocks were stopt, and a few things were thrown from shelves. Top-heavy 
statuettes tipt over. All sleepers were awakened. Things generally moved north and 
south, or northwest and southeast, which seemed to be the general impression of the 
direction. 

Bethany, San Joaquin County (Mr. Schichtman). —'The movement was from north- 
east to southwest, and was sufficient to splash water from a full trough, but not strong 
enough to overthrow objects. 

Byron Hot Springs, Contra Costa County. — The springs, some 30 in number, hot and 
cold, were not affected by the earthquake. One chimney and some plaster were cracked 
and a picture was thrown from the wall. The shock was considered quite severe, though 
the damage was slight. 

Tracy (R. Crandall). — Tracy, in the San Joaquin Valley, lies at the foot of the range 
separating Livermore Valley from San Joaquin Valley. The shock was not at all severe ; 
in fact it was spoken of by several as being no heavier than the jarring often occasioned 
by heavy engines starting a loaded train. Very few objects fell, and in only one case 
was any damage done to a building. This was the cracking of a 2-story brick build- 
ing which did not appear to be especially well constructed. Only one brick chimney 
cracked, and none fell; so it would appear that the building cracked because of the 
poor construction rather than because of the intensity of the earthquake. Milk or 
water was spilt in only few cases —not over 30 per cent. The water-tank of the 
Southern Pacific railroad at Tracy fell, as did similar tanks at Livermore, Pleasanton, 
and Lathrop. ‘The reason for this is explained in the description on a preceding page 
of the construction of the tank supports at Niles. 

Lathrop (R. Crandall). — This is a small town upon the floor of the San Joaquin Valley, 
about 12 miles east of Tracy. The intensity was about the same as at Tracy. There 
was no appreciable difference in the number of fallen objects or stopt clocks, the main 
difference being that a considerable number of people were not alarmed enough to get 
up. One man who was up experienced no difficulty in standing or walking. The 
general impression is that the shock was slightly lighter than at Tracy, 

Stockton (R. Crandall). — Stockton is about 10 miles north of Lathrop, but not much 
farther east. As it is a much larger place, it was easier to sce the effects of the earth- 
quake. Not as much detailed work was done in Stockton as at the other places, since 
it was known that Mr. Edward Hughes was collecting data in that city. The shock 
was felt with alarm by people in houses and on the ground. The motion was spoken of as 
being a rolling motion like that felt on board ship. Almost no objects fell, even in houses 
where there were tall vases and similar bric-d-brac. At one drug store two little vials 
fell from the shelves; at another even built-up pyramids of various articles for window 
display were undisturbed. Milk and water were spilt in a very few cases. Splashing 
of milk up the sides of the pans was noted by a few persons, and the direction was given 
as northwest and southeast. Many clocks were stopt, but there was nothing consistent 
in the direction of pendulum motion. All of the big brick buildings were visited, and 
no damage was found except in an old 2-story building which seemed merely to have 


312 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


had an old crack widened, due to the settling of the foundation. The City Hall had 
considerable plaster cracked, but this was due to the swaying of a 50,000-gallon tank 
on the roof. Three chimneys were cracked, and one was reported to have fallen, but 
this was not verified. At the houses where the chimneys were cracked, milk was not 
spilt from open pans, so it is apparent that the chimneys were faulty and not that the 
earthquake was severe. 

(E. Hughes.) —A careful and exhaustive inquiry was made at Stockton by Mr. Edward 
Hughes, under the direction of Prof. J. C. Branner, and the following notes are con- 
tributed by him: 

The shock, while strong enough to alarm many of our people, was chiefly notable for 
the absence of the destructive effects experienced in many less fortunate localities. It 
began with a gentle trembling motion, which increased slowly for the first 5 or 6 seconds, 
then rapidly to a maximum of rough jolting shocks lasting perhaps 5 seconds. These 
were followed by a series of long, smooth vibrations, which gradually decreased in am- 
plitude until no longer perceptible. The effects, as noted by many observers, would 
indicate that the heavier shocks traveled in a northwest-southeast direction, while the 
smooth oscillations which marked the latter part of the disturbance ran nearly east- 
west. The immediate effects, as noted in dwellings, during the shock were the creak- 
ing and straining of buildings, the swinging of doors, the rattling of window weights 
and pictures on the walls, the swinging of chandeliers and drop-lights, and the stopping 
of clocks. Out of doors, some observers claim to have noticed the swaying of tall build- 
ings and smoke-stacks; and many mention the violent motion of the trees, the branches 
of which lasht together as if in a storm. Birds frightened from their resting places flew 
in confusion, and the air was filled with their startled cries. 

A careful canvass of the city gives the following results in the way of damages sus- 
tained: There were a few small cracks in the arches in the-hallways of the county court- 
house. It is safe to attribute this to faulty construction rather than to the violence of 
the shock, as a number of large cracks had opened in various parts of the building soon 
after it was finished. One water-tank was overturned, the supporting framework being 
insufficiently braced; this tank fell about 15° east of south. 

A large gasometer at the natural gas well on north Commerce Street was slightly 
damaged. Castings supporting the guide wheels were broken, and the gas tank was 
slightly twisted to the left so that the guide wheels were thrown off the guides. 

In two or three cases in the city, the tops of chimneys fell off. Examination showed 
that the mortar had never properly united with the bricks, owing probably to their 
dryness when laid. In several cases houses suffered damage by the spilling of water 
from attic tanks. 

Aside from these cases of relatively insignificant damage, everything gives testimony 
to the comparative gentleness of the shock. In china stores, where fragile wares were 
displayed in all sorts of insecure positions, not a piece was displaced or broken. So 
far as can be learned, no plaster fell anywhere in the city, and there was no breakage 
of bric-a-brac or china in the dwellings. Observers who watched the minute hands of 
clocks that were not stopt estimate the duration of the shock at from 30 to 40 seconds. 

The heavier shocks were undoubtedly from northwest to southeast. This was shown 
in several ways. Tanks spilt water in both these directions, and the tank noted above 
fell nearly to the southeast, although its frame ran approximately east and west, and so 
offered some resistance to free motion to the southeast. In McCloud’s Lake, the waves 
ran northwest-southeast, breaking highest on the bank and bulkhead in the southeast 
corner, while the north side was little affected. At the city pumping station on Mormon 
Channel, a similar effect was noted. Several observers claim to have seen tall buildings 
and stacks swaying in the direction indicated, and those who were standing were con- 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 313 


scious of the movement of their own bodies in the same direction. Milk in open vessels 
left a coating of cream highest on the northwest and southeast sides, although in many 
cases motion was also shown east and west. 

While there is not entire agreement with reference to the east and west vibrations 
during the latter part of the shock, the larger number of observers plainly felt and saw 
their effects, and the evidence as to their occurrence seems conclusive. Doors swung 
east and west; swinging objects, such as drop-lights, hanging baskets, etc., were found 
either swinging east and west or in circles after the shock, and pictures hung on north 
and south walls of rooms showed lateral motion during the latter part of it. Tanks in 
several cases spilt water east and west, although not in such quantities as in the other 
directions. 

The following table indicates the effect of the shock on the 128 clocks concerning which 
reports were received : 











Orientation. abt ceitee Stopt. Not Stopt. 
Facing west . . 32 17 1b 
Facing north . . 36 18 18 
Facing east .. 27 13 14 
Facing south . . 33 16 ity 

LOtala eae sans 128 64 64 

















Clocks with very long or very short pendulums were generally not stopt. Two town 
clocks were not stopt. One of these, which, through the courtesy of Mr. E. B. Condy, 
I was permitted to examine, is in the tower of the county court-house. Its frame stands 
northeast and southwest; and its 100-pound pendulum, hung on the northwest side of 
the frame, swings northeast and southwest, missing the edge of the iron stand about 
0.5 inch. A deep scar in the mahogany pendulum bar indicates that during the shock 
the pendulum swung sharply to the southeast, its bar striking the edge of the iron stand. 
The weights of the same clock hang in a narrow shaft at the side of the tower. The 
wire pulley cords which support the weights were found so badly twisted as to interfere 
with winding the clock a day or two after the earthquake. On the inside of many 
clock-cases are found scars made by the striking of the pendulums. These scars are 
deepest on the south side in clocks facing east or west, and on the west side in clocks 
facing north or south. 

Some persons who were outdoors during the shock claim to have heard a dull rumbling 
sound immediately preceding it. They find it difficult to describe the sound accurately, 
and in some cases think it may have emanated from nearby buildings. A considerable 
number of people suffered from nausea and dizziness, with headache, for a time after the 
shock. With some these disagreeable symptoms persisted all the following day. 

Farmington, San Joaquin County (J. F. Gwin). — The house quivered, then the sash 
weights of the windows began striking back and forth, and a heavy rolling motion was 
felt which caused open doors to swing back and forth. The clock stopt. The surface of 
the ground moved in waves like water, and trees moved with the ground. 

Central San Joaquin County (E. P. Higby). — In Ranges 6 and 7 E., townships 1 and 
2.N., Mount Diablo Meridian and Base line, there were apparently 2 maxima of equal in- 
tensity with intervals of a few seconds between. The apparent direction was SW. to NE. 
No objects nor chimneys were overthrown. The bed shook, and chandeliers, pictures, open 
doors and shutters were caused to swing. Windows and window weights rattled. The 
clock did not stop. Paper on the walls was cracked. The slate roof on a high church 
tower was cracked. There was scarcely a breath of wind, yet large trees swayed and bent 
as if rocked by a terrible gale. Water in the wind-mill tank and in other tanks slopt 


314 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


over, and continued to do so for 5 minutes after the shock. Water was thrown from a 
swimming tank where the level was 5 feet below the top of the tank; water at one place 
in the river was thrown over a concrete wall 8 or 9 feet high. 

Modesto (i. Hughes). — In common with other points in the great interior valley 
region, Modesto received a very decided shaking up by the earthquake, but suffered 
practically no damage. The local effects were the stopping of clocks, the swaying of trees, 
hanging baskets, drop-lights, and chandeliers; and in a few cases the fall of objects from 
insecure positions-in stores and dwellings. Water tanks and troughs, milk pans, etc., 
spilt part of their contents, and in one or two instances cracks opened in buildings. 
No one, so far as known, actually timed the duration of the shock in seconds. 

The observations of many persons in and near the town indicate that the vibrations 
were in two principal directions: viz., northwest-southeast and approximately west-east. 
The heavier shock seems to have been in the first direction, but observers are not in entire 
agreement on this point. Clocks of larger size were quite generally stopt, no matter in 
what direction they faced. Several persons report having heard a roaring or rumbling 
sound, beginning a few seconds before and continuing until the end of the disturbance; 
and a number of people were affected by symptoms somewhat like seasickness for several 
hours after it. 

The following detailed notes were obtained from citizens of Modesto and vicinity: 

(Mr. Schaffer.) —Trees swayed northwest-southeast. ‘‘The Swan,” a new building 
with green walls, cracked at the junction of the ceiling with the northeast end wall; also 
at the junction of the ceiling with the fire-wall running thru the center of the building from 
northwest to southeast. The cracks in both cases were on the second (the top) floor. 
The building faces northwest. 

(Player’s Drug Store.) — Boxes on shelves on the northwest side of the store fell toward 
the southeast. 

(Mr. Swanson.) —Saw water spilt southeast-northwest from the railway tank at the 
depot. 

(Al Fogarty.) —Meat market. Mr. Fogarty ran from the building, and on returning 
after the shock he found drop-lights and a butchers’ scale, suspended by a single wire 
from the ceiling, swinging in a direction parallel with the street, northwest-southeast. 

(Green Brothers.) — Heard a roaring sound just before the shock. Felt the bed swing 
northwest-southeast. Plaster sifted down from cracks in the ceiling. 

(Ei. E. Woods.)—Mirror hanging from southeast wall fell, on account of breaking of 
the cord, on its face toward the northwest. 

(Mr. Chapman.) — Ranch 5 miles southwest of Modesto. Water trough oriented north- 
south spilt water from both ends. 

(George T. McCabe.) —The bed was standing north-south. The first motion was east- 
west, the second and maximum motion was northwest-southeast. Trees swayed north- 
west-southeast. The window sash dropt. 

(Mr. Rider.)—Water in the street gutters moved west-east in the first part of the 
shock; in the second part, northwest-southeast. 

(Mr. Schaffer.) —Twenty-one miles southeast of Modesto. The sliding doors on a barn 
fronting east moved north and south repeatedly during the shock. A water trough a 
few feet away spilt water east and west. 

(Johnson and Ross Store.) —A pile of paint cans stood northwest-southeast. Several 
cans fell to the northeast. 

(G. W. Elsey.)—A tall, open-framed “ Mission” clock facing southeast was found after 
the shock with its pendulum lodged on the top of a cross-bar of the frame. The position 
of the pendulum indicated a considerable increase in the amplitude of its vibration north- 
east-southwest in order to allow it to swing high enough to lodge. There were several 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 315 


similar cases of lodged pendulums in clocks facing in the same direction. Mr. E. Elsey 
also noted a water-tank spilt east and west, and trees swayed in the same direction. 
He heard a rumbling sound. 

(H. Hintze.)—A water-tank spilt east and west. A hanging lamp swung in the 
same direction, dropping its chimney to the east. A bed on the porch rolled east and 
west. He heard a rumbling sound during the shock. 

(Editor of the Daily Herald.) —Bed moved northwest-southeast. 

(Farmers’ and Merchants’ Bank.) —'The vault is built upon a foundation independent 
of the rest of the building. The front of the vault, facing southwest, is continuous with 
a lath and plaster partition which extends to the ceiling. On the left is a wash-room, and 
on the right an opening into the room at the side and back of the vault. The plaster 
partition is cracked where it Joins the top of the vault and part way down the sides, proba- 
bly indicating a greater amplitude of motion in the building than in the more solidly 
constructed vault. 

(W. A. Harter.) —At Ceres, 6 miles south of Modesto, a tank spilt north-south. 

(W. R. High.) —One mile north of Modesto, a tank spilt north and south during the 
early part of the shock, and east and west later. Trees swayed north-south. 

(Empire Stables.) — Drop-lights swung and water in trough spilt northwest-southeast. 

(A. L. Holtham.)—Milk pans on shelf supported by wires spilt milk west. The 
shock was preceded by a roaring sound. 

(Modesto Gas Works.)—Water in the gasometer tanks spilt northwest-southeast. 
A chandelier in the building hung by a 0.375 inch gas-pipe 12 feet long; after the shock 
was over this chandelier was swinging northeast-southwest. 

(J. T. McNeely.) —Station agent saw the railroad water-tank spill northwest-southeast. 

(Editor of the News).—A water-tank belonging to J. Urie, 2.5 miles southwest of Mo- 
desto, was overthrown to the west. 

The following were the clock records at Modesto: 








Number of 














Orientation. Clocks. Stopt. Not Stopt. 
Facing northeast . 4 3 1 
Facing southeast . 12 9 3 
Facing southwest . 7 5 2 
Facing northwest . 7 at 3 

Total 30 21 9 











Ceres, Stanislaus County. — The shock was felt, but is reported as not severe. 

Oakdale, Stanislaus County (F. G. Keid).— The shock seemed to be in a northeast 
and southwest direction. In the school-house, a 2-story brick building, timbers lying 
in a northeast and southwest direction were loosened from the concrete at the ends, but 
those extending normal to this were not affected. Clocks stopt. 

(E. C. Crawford.) —A flag-pole 110 feet high swayed apparently north and south; 2 
clocks stopt; water in a tub moved north and south; and a stand lamp seemed to tip 
slightly north and south until steadied; but no objects were overturned. 

Westley, Stanislaus County (W. G. Carey). — The town is on adobe soil with gravel at 
a depth of 20 feet. Furniture and pianos were moved across floors from the walls toward 
the south, and quite a number of pieces of furniture were toppled over. No chimneys 
were damaged, but several large water-tanks were demolished. These demolished water- 
tanks thru the country seem to have been rotated about one-fifth counter-clockwise. 
Cars on the track were moved at least a foot. At the railway depot, a 1,400-pound iron 
wheel was rolled back and forth for a distance of 9 feet northwest and southeast. There 


316 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


were 2 maxima in the movement of the earth, and the second was the stronger. Some 
men sleeping on a scow on the river 2 miles east of Westley heard a rumbling sound before 
any shock was felt, and came out of the scow to see what it was. Then the shock came 
and the waters rolled and foamed. 


COAST RANGES EAST OF THE RIFT AND SOUTH OF MOUNT HAMILTON, AND THE 
WEST SIDE OF THE SAN JOAQUIN VALLEY FROM WESTLEY TO DUDLEY. 


In the coast ranges on the east side of the Rift, south of Mount Hamilton, and along 
the west side of the San Joaquin Valley, settlements are few and widely scattered, so that 
opportunities for obtaining data as to the distribution of intensity were correspondingly 
rare. This territory was examined by Mr. G. F. Zoffman, under the direction of Prof. 
J. C. Branner, and the results of his observations and of others are embodied in the 
following report: 

Pacheco Pass Road. — Starting from Hollister, the county seat of San Benito County, 
the writer went up the Pacheco Pass road over the Mount Hamilton range to Los Banos, 
in the San Joaquin Valley. There are but few brick or stone chimneys in this neighbor- 
hood, and inquiries were directed to the splashing of milk and the falling of dishes and 
other movable objects. At the entrance to the canyon thru which the road winds, 
several houses were visited. Only a few dishes had been broken and milk was thrown 
only from pans well filled. At Bell’s Station no damage was done beyond the loss of 
milk. High bottles and dishes standing upon shelves were uninjured. The residents 
say that the vibrations were from east to west, and had a rocking motion. Before the 
shock a rumble was distinctly heard coming from the west. 

At ranch-houses about 5 miles northwest of Bell’s Station, and farther up in the moun- 
tains, the shock was of considerably less intensity. 

Mountain House. —'The shock was reported as having been very mild; no dishes were 
thrown from shelves, nor milk splashed from pans. The proprietor states that the 
earthquake began with a north and south movement which later changed to the east and 
west. The shock here should be rated at V. 

Going down into the valley on the east side of the Pacheco Pass the intensity of the 
shock perceptibly increased. At a ranch house 7 miles from the pass, nearly all the milk 
was thrown from pans and all the water from tanks. In a well where the water was 7 feet 
from the surface, some was thrown out. As noted by one gentleman, water was thrown 
from a tank, first from north to south, changing later to east and west. 

San Luis Ranch. — At the east end of the valley, on the San Luis Ranch, Mr. Mills 
stated that he distinctly felt the vibrations begin from north to south; there was then a 
lull of a few seconds and then followed a very noticeable east and west movement. The 
surface of the ground is said to have moved up and down like the waves of the ocean. 
Thruout this valley, which is made up of gravels deposited on firmer rocks beneath, the 
shock appears to have been nearly uniform. 

Los Banos. — On emerging from mountainous districts into the deep alluvial plains 
of the San Joaquin Valley, the intensity of the shock increased, until at Los Banos it 
reached a maximum. <A count of the chimneys showed 57 per cent (17 out of 30) fallen. 
All the brick chimneys were damaged, as shown by the accompanying photographs. 
(Plate 1238, c.) A peculiar feature of the effect upon these structures was that. all the 
damage was on the northeast and southwest sides. Frame buildings were not damaged 
beyond the falling of plaster, or the throwing down of chimneys. According to the 
statements of the residents, and the data obtainable, the vibrations were north and south. 

Volta. — Out of 7 chimneys 6 were thrown down by the shock. The plaster in frame 
houses was considerably damaged, but none of the buildings was thrown from its 


123 


PLATE 








Bridge over Salinas River, 4 miles south of Salinas. South terminal pier thrust south 7 feet. 
A.C. L. 


C. Los Banos Bank. W. L. 


B. Los Banos Hotel. 


D. Coalinga, 





W.L. 


Z. 


” 
Ul i i 
JMIVERSTTY OF WLilAOTS 


. 


ey wars Wat dnis alte w faro fan 





ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 317 


foundations. The town had no brick structures. The water of the nearby irrigation 
canals had, in places, been thrown up on the banks as much as 6 feet above the usual level. 

Newman. — From Los Banos toward Newman the intensity of the shock appears to 
have decreased. At the latter place, out of 8 brick buildings only one, just constructed, 
was thrown down; one was cracked, while the remaining 6 were undamaged beyond the 
falling of a little plaster. Sixty per cent (36 out of 60) of all the brick chimneys fell, 
altho little other damage was done to frame houses. A man who saw the 53,000-gallon 
railroad water-tank fall stated that at the beginning of the shock it began to sway north 
and south, changing later to east and west, and finally falling toward the west. 

Crow’s Landing. — Out of 18 chimneys only 3, or 162 per cent, fell. Considerable 
water was thrown from the tanks. At a brick oil-pumping station about 4 miles north 
of Crow’s Landing a few cracks were made in the walls. The large oil-tanks and water- 
tanks were undamaged. People in this neighborhood state that the direction of the 
vibrations was first from north to south, changing later to east and west. Opinions differ 
on this point. Many also state that a circular motion was perceptible. 

Grayson and Westley. — The town of Grayson is on the banks of the San J oaquin River. 
No damage was done by the earthquake. A very few things were thrown from the shelves, 
but no chimneys were thrown down. At Westley all the chimneys were found intact. 
One poorly braced railroad water-tank fell, and one remained standing. The people in 
this district maintain that the direction of greatest intensity was north and south. 

From Westley to Mount Hamilton. — From Westley the writer traveled up the Arroyo 
del Puerto over into San Antonio and Santa Isabel Valleys and up to Mount Hamilton. 
There are but few houses on the east side of the summit, and but little data was collected. 
The best was obtained at the Phoenix Quicksilver Mine. Here there are several brick 
buildings and chimneys, but no damage at all was done to them by the earthquake. In 
the tunnel there was no shifting of strata. At Mount Hamilton Observatory a couple of 
chimneys were cracked, but none fell. From Mount Hamilton, the writer went to 
Paicenes, in San Benito County, thru the Panoche Valley to Mendota, thence to Coalinga, 
Dudley, Cholame, and Peachtree. 

Paicenes. — Going from Hollister toward Paicenes the intensity of the earthquake 
rapidly decreased. At the latter place, which is on the gravels deposited by Tres Pinos 
Creek, none of the chimneys (3 in number) were damaged, nor were the clocks stopt. 
Water and milk were thrown from their receptacles in an east and west direction. 

Elkhorn. — At the Elkhorn roadhouse there were 3 clocks; the one facing north was 
undisturbed, while the other 2, one facing south and the other east, stopt. No water 
was thrown from the troughs nor milk from the pans. A few miles northwest of Elk- 
horn, the milk was thrown from pans on the northwest and southeast sides. The infor- 
mation obtained from the residents in regard to the direction of the vibrations was very 
contradictory. 

Emmet Post-office. — At Emmet milk was thrown out in small quantities, but no 
movable objects were moved or upset. Near the summit between Tres Pinos Creek 
and the Panoche Valley, the shock was so slight that people did not think of arising. 
Nothing was thrown over, nor was milk splasht from pans. From Paicenes, where the 
intensity may be rated at about VI, it gradually decreased up Tres Pinos Creek until at 
its source the intensity was about IV. 

Panoche Valley. — This region lies on the east side of the Coast Ranges. At the head 
of the valley the shock was so slight that some of the inhabitants were not awakened. 
On going farther down into the lower ground where the soil is deeper, the intensity was 
slightly greater. At the Panoche store water was thrown from the tank, but no dishes 
were broken. After leaving Panoche Valley, no definite information was obtainable 
before arriving at the Chainey Ranch 14 miles west of Mendota. This ranch is on the 


318 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


plains on the west side of the San Joaquin Valley. The superintendent said that water 
was thrown out of troughs in a northeast and southwest direction. Movable objects 
were not disturbed. 

Mendota. — Mendota is on the low alkali plains on the west side of the San Joaquin 
River in Fresno County. The intensity of the shock was comparatively light. In the 
town there were 17 brick chimneys and not one was thrown down. The railroad tank, 
two-thirds full of water at the time, was shaken down; but it was very insecurely built 
and only a very small vibration was necessary to overthrow it. Bottles and other unstable 
articles were not disturbed. The proprietor of one of the hotels, who was up, stated 
that the first movement was east and west, the second north and south, terminating 
with a decided twist. People who observed the plains at the time said that they assumed 
a wave-like appearance, and that trains rose and fell as the undulations past beneath 
the tracks. They also state that this wave motion was confined to the north and south 
movement, the east and west motion being more in the nature of a tremor. In the irri- 
gated lands south of Mendota, considerable water was thrown from the canals. 

Mendota to Coalinga. — At an oil-pumping station 10 miles south of Mendota, there 
were 10 large tanks; of these the roofs (unsubstantially braced) of 6 caved in, and much 
oil was thrown over the sides. The brickwork of the furnaces was not cracked. At 
the ranch-houses, about 6 miles east of the pumping plant, milk and water were thrown 
from their receptacles, and considerable damage was done by the breaking out of the 
head gates in the canals. The direction of greatest intensity is said to have been east 
and west. Many people in this region suffered from a nauseating sensation following 
the quake. 

Coalinga. —'The tops of a few of the walls of brick buildings were slightly damaged, 
as shown by the accompanying photograph. (Plate 123p.) A few dishes and bottles 
were thrown from the shelves, and water was slopt out of the tanks, but none cap- 
sized. The direction of greatest intensity of the vibrations was northeast-southwest. 
At the oil wells no damage was done either to wells or pipe lines. At a pumping station, 
the brick lining of the furnace was cracked slightly. Considerable oil was thrown from 
the tanks. In a large reservoir containing No. 10 oil (very heavy), the oil was thrown 
up 10 inches on the northeast and southwest sides. In a pump having No. 16 grade, 
the oil was splasht 3 feet up the sides. 

Dudley. — Going south from Coalinga thru the Kettleman plains, the intensity of 
the shock apparently decreased, tho there were so few inhabitants that it was impossible 
to get definite data. At Dudley Station (a farm-house) nothing on the shelves was 
disturbed nor had milk or water slopt over. It was evident that the earthquake 
was less intense than at Coalinga. Entering the mountains west of Dudley, there was 
a further decrease in the intensity. 

Cholame. — At the east side of the Cholame Valley, the occupants of a ranch-house 
had not felt the shock. At Cholame Post-office the shock was felt, but very slightly. 
The postmaster stated that it had a rocking sensation rather than a shaking one. At 
the Cholame ranch a mud chimney about 7 feet high was left standing out by itself 5: 
unharmed, but very insecure. 

Parkfield.—Near Parkfield there are fissures in the earth, bearing N. 45° W., known 
to have existed since the first coming of white men. In some places the depressions are 
35 feet deep. These fissures were not reopened at the time of the late earthquake. 

Stone Canyon Coal Mine. — At the coal mine the shock was very noticeable. The 
fireman on duty the morning of the earthquake stated that the smoke-stacks, 35 feet 
high and guyed, swung considerably in various directions. No shifting occurred in the 
strata of the underground workings. It was stated that the movement was northeast 
and southwest. 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY, 319 


Peachtree. — As Peachtree was approached, there was a perceptible rise in the inten- 
sity. About 2 miles east of the post-office, dishes had been thrown over and milk spilt 
from pans. At the station itself, however, nothing had been overturned. The region 
visited between Cholame and Peachtree is in small valleys lying in the mountains on the 
west side of the Salinas Valley. The soil is nowhere deep. 

Cantua Creek, Fresno County (8. C. Lillis). — The shock was severely felt in this region, 
and its direction was southeast-northwest. A series of landslides caused by the earth- 
quake were reported by Mr. Lillis, extending from the northwest corner of T. ISHED. 
14 E., M.D.M. to the middle part of T. 15, R. 11 E., a distance of about 23 miles. The 
features were not at first recognized by Mr. Lillis as landslides, and as they occurred on 
the east side of the Coast Ranges, on the border of a portion of the San Joaquin Valley, 
where the intensity was abnormally high, the hypothesis was entertained that there 
might have been a supplementary fault in that region along the edge of the mountain 
range. ‘The remarkable alinement of the features lent support to this suggestion. The 
region was, however, subsequently visited by Prof. G. D. Louderback, in company with 
Mr. Lillis, and the features reported by the latter were found to be landslides. Pro- 
fessor Louderback furnishes the following note regarding them: 


The phenomena reported by Mr. Lillis are several landslides. In each case the effect of 
the movement can be followed in detail and sharply delimited. The form of the moved body 
is typically that of the landslide in each case, with the cliff at the upper end curved and 
concave toward the lower part of the slope. The mass has moved away and downward, 
leaving in some instances an open space or fissure, partially filled at the present time (May, 
1907) by caving. The back cliffs, followed around, gradually pass into lateral planes of 
movement, which themselves are sometimes gaping on the more elevated side, showing a 
forward and slightly lateral movement of the mass. (See plate 125B.) 

No general fissure, fault, or rift was observed passing thru or near these landslides, altho 
a careful search was made for such features. I suspected at first that there might be such a 
rift-line, because the landslides are approximately along one line or belt. This appears, 
however, to be due to the fact that one particular formation is especially favorable to land- 
sliding, all the slides that I saw along the lower part of the range being associated with a 
thick reddish-brown shale of a definite stratigraphic horizon (Tejon?). The general struc- 
ture of the range causes the rocks of any given horizon to outcrop along a line roughly 
parallel to the range front (approximately northwest-southeast). The landslides all lookt 
fresh, and according to Mr. Lillis several of them (and probably all of those under con- 
sideration) were caused on April 18, 1906. I made a trip across the hills from the valley 
to New Idria and noted nothing that appeared to be a recent seismic line. 


EAST SIDE OF THE SAN JOAQUIN VALLEY SOUTH OF MODESTO AND THE ADJACENT 
PORTIONS OF THE SIERRA NEVADA. 


In this region information regarding the intensity of the shock is rather scant. The 
shock was in general not sufficiently severe to excite alarm, and people as a rule did not 
note carefully its effects at the time. Such records as are available indicate that an 
intensity ranging from VI to V prevailed to the eastern edge of the valley, but that it 
died out rapidly in the mountains beyond. 

Merced, Merced County. — Clocks generally were stopt, and hanging objects were 
caused to swing. One chandelier was observed to swing north and south, and then in 
a circle. 

Madera, Madera County (F. E. Smith). — The principal disturbance was preceded 
by a tremulous motion for about 10 seconds. There were 2 maxima in the principal 
disturbance, the second being the stronger; and a tremulous movement succeeded it. 
The apparent direction of the movement was from southeast to northwest, and objects 
were overturned toward the northwest. The duration of the shock was thought to be 2 


320 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


minutes. It was severe enough to rattle windows and move doors; to cause the bed 
to move; to swing hanging objects and stop clocks; and to overthrow ornaments, vases, 
etc., but not to throw chimneys. In other parts of Madera County the shock was reported 
from Daulton, Magnet, and Gold, but without sufficient details to afford a clear idea of 
the intensity of the shock. 

Fresno, Fresno County (A. C. Olney). — No. VI of the Rossi-Forel scale describes 
conditions here quite accurately. There was a general awakening of sleepers, oscilla- 
tion of chandeliers, stopping of clocks, and considerable agitation of trees. Some people 
ran out of their houses. Water in troughs was spilt out, ete. No damage was done 
to buildings. 

(J. P. Bolton, observer of the U.S. Weather Bureau.) — At the time of the earthquake 
Mr. Bolton was on the third floor, standing near a window. The time of the shock was 
5" 13" 30°. The first shock lasted about 10 seconds. It stopt clocks, swayed build- 
ings, gasoliers, furniture, unlocked-doors, window-weights and shutters. There was a 
short interval of cessation, then a second shock which lasted about 30 seconds, but was 
less severe than the first. It had a tremulous motion which gradually died away. Each 
shock developed its greatest intensity near its beginning. The apparent direction was 
from south to north. The intensity of the first shock was sufficient to sway the stoutest 
building and disturb its contents without displacing them, and to damage walls slightly. 
The only sound observed was that caused by the jarring of the building, ete. Many 
dogs barked vigorously shortly before the first shock. 

Reedley, Fresno County (John Fairwether).—The shock was north and south ; 
clocks stopt; some plaster was cracked, but no chimneys fell; a front door which was 
locked was caused to swing open. At Conejo water was slopt out of ditches to the 
north for 40 feet. At Jameson 2 distinct shocks were felt. At Riverdale, hanging 
objects were caused to swing. At Kingsbury, a slight shock was felt. At Fowler 3 
wells were filled with sand. At Sanger a clock was stopt. 

Visalia, Tulare County (F. A. Swanger). — A rocking-chair rocked vigorously north- 
east and southwest, but no shifting of the chair was observed as it rocked. The swell 
and fall of the earth-wave seemed strong. 

(A. M. Doty.) —Four shocks were felt in Visalia, the last being the most pronounced. 
The town clock and almost all pendulum clocks in the city stopt. The vibration was 
from north to south. The Delta Building, a two-story brick structure, swayed to the 
south so perceptibly that it seemed difficult for it to regain its equilibrium. When it 
did sway back, the tin roof rattled as if some one were pounding on it with a hammer. 
Practically everybody in Visalia was aroused from sleep by the quake. 

Dinuba, Tulare County (Miss L. H. Tindall). — There was a smart shock. A clock 
at the bank stopt. A crack in a brick building was so enlarged that the wall had to be 
strengthened by rods. A chandelier swayed from south of southwest to north of north- 
east. Elsewhere in Tulare County shocks were reported at Exter, Kaweah, Orosi, 
Porterville, and Tulare. 

Bakersfield, Kern County (A. G. Grant).—The shock was strong enough to rattle 
windows and doors. Oil slopt out of tanks in the oil-fields 5 miles to the northeast 
of the city. Some clocks are reported to have stopt. 

Isabella, Kern County (Stephen Barton). — Mr. E. King, lying in bed, noticed the 
swinging of a pistol seabbard suspended by a strap directly over his head. 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 321 


EAST OF THE SIERRA NEVADA. 


Data CoLLEcTED BY Gro. D. LoupERBACK. 


General note. —In the towns along the east base of the Sierra Nevada and within 25 or 
30 miles of the base, the shock was distinctly felt, movable objects were seen to swing 
and heard to bump or rattle, and a very small number of persons were awakened. 
Farther east the most notable feature of the reports is that wherever the effects of the 
earthquake were made evident, the physical signs, such as the swinging of suspended 
objects, etc., were described almost to the exclusion of direct physiological effects. This 
is apparently at variance with the principles upon which the Rossi-Forel scale is founded, 
as the first 3 grades of intensity, beginning with the lowest, are based on feeling; the 
visible disturbance of objects not beginning until grade IV is reached. This may be 
due entirely or chiefly to the following conditions: Settlements are few and far between 
and many contain a very small number of inhabitants. When the earthquake occurred, 
the great majority were asleep, and the few who were up were moving about at active 
work and were in general not of a sensitive type. It is therefore probably impossible 
to get satisfactory and correct statistics indicating the distribution of the zones of inten- 
sity of the first 3 grades; and the sensible effects of the earthquake probably extended 
much farther east than reported. 

Perhaps the most important of the physical signs reported is the disturbance of smooth 
water surfaces. In five instances, at three different localities, ditch tenders or irrigators 
noticed an agitation of quiet water surfaces and that the water lightly splasht against 
the sides as if from low waves, or as in a vessel of water when it is slightly tilted. As 
the morning was clear and entirely without wind, it imprest them as peculiar, and the 
matter was reported when they went to breakfast. The suggestion of one that some- 
thing peculiar had happened, and of another that it was an earthquake, was each in its 
place the incitement of sallies of wit at the expense of the reporters. When news of 
the California earthquake reached these places several hours afterward, the time was 
found to agree as closely as determinable with the phenomena of the morning. In each 
of these cases, however, it was reported that no shock was felt. It is suggested that 
with moderately long waves such surfaces may prove very sensitive indicators of inten- 
sities down to the lowest degree on the scale. 

The farthest point east at which earthquake effects were reported was Winnemucea, 
about 340 miles from the fault. A careful search was made for persons who had felt or 
seen indications of the shock. Only one apparently authentic case was found, and that 
was of a nurse who had retired a little after 5 o’clock, after a night’s work at the County 
Hospital. She was lying quietly in bed and felt no disturbance whatever; but noticed 
a hanging lamp swing gently back and forth. Careful inquiry at newspaper offices, 
the telephone office, the post-office, and of the railroad agent, the weather bureau ob- 
server, and many individuals in different parts of the town, failed to discover another 
observation. ‘This is rather remarkable, because Winnemucca is a town of considerably 
over 1,000 inhabitants. It is believed that the one definite report obtained is correct; 
and, as corroborative testimony, may be added the reports from two other localities 
almost as far east as Winnemucca, in which similar phenomena were described (in one 
the disturbance of a water surface, in the other a swinging lamp), with the further simi- 
larity that no shock was felt. 

The elongation of the intensity zones in a northwest-southeast direction is marked. 
The strongest effects east of the Sierra Nevada were felt with practically the same in- 
tensity from at least Sierra Valley to Lone Pine (about 250 miles along the range), while 
50 miles east of the Sierra the intensity had materially lessened, and 100 miles east 


pe 


S22 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


reports are practically unobtainable. This agrees, of course, with the elongation of the 
locus of disturbance. 

It also appears probable that the sensible effects extended farther along Humboldt 
Valley, which is practically parallel to the direction of propagation, than along those 
lines where successive mountain ranges were thrown across the advancing waves, as in the 
southern Nevada region. 

In most cases the direction of vibration was given as north-south, or northwest-south- 
east; tho in two or three cases north of west to south of east, or east-west, directions were 
given. Most of the clocks reported stopt faced north or south; a few faced west. 

In a few cases the statement was made that there were two shocks very close together, 
but most of the observers did not distinguish more than one. 

Details for the various localities follow: 

Round Hole, 70 miles north of Reno (F. MeMillan). — A distinct earthquake was felt 
which lasted several seconds. 

Peavine Mountain. — A number of ranchers and miners were up at the time of the earth- 
quake, on the north side of Peavine, about 10 or 12 miles northwest of Reno. No one 
noticed the shock nor any indications of it. 

Reno. — The shock was distinctly felt by a number of persons. Some were awakened. 
The great majority knew nothing of it. A good account was given by Mr. Jensen, of 
the U. 8. Weather Bureau. He was in the office to take instrumental readings. The 
office is on the fourth floor of a rectangular brick building, longer east-west than north- 
south. He heard some pictures rattle and thought the janitor was getting remarkably 
industrious downstairs; then he noticed that they were all rattling and surmised that it 
was an earthquake. His attention was attracted to an electric bulb on a long wire hang- 
ing from the ceiling, only a few inches from the west wall. It was swinging so as to hit a 
metal nipple on a pipe in the wall, thus making quite a noise. The building seemed to 
shake east-west. 

Olinghouse. — Many were interviewed, but none had felt the shock. While there are 
one or two vague reports, it is probable that no one really felt the effects at this place. 

Wadsworth. — A canvass failed to elicit any definite account. 'The postmaster claimed 
he talked with many people, but knew of none who had observed the shock. 

Hazen. — Quite a number of people were interviewed, but no good definite account could 
be obtained. Most people decidedly had not felt it, and were not sure of any one who had. 
There were one or two hazy reports of persons who were supposed to have felt or observed 
it, and one man admitted having noticed a “light shock.” 

Virginia City. — Only a few persons noticed the shock. Mr. D. T. Smith was sleeping 
on the third floor of a rectangular building that stands east and west. He woke up and 
felt a movement of the building. An electric globe suspended by a cord from the ceiling 
(about 5 feet) swayed about 1.5 inches with an elliptical movement, the major axis a 
little north of west. No one else in the building noticed it. 

Wabuska. — A few are reported as feeling a “jar.” No one noticed the direction. 

Yerington. — A few felt the shock. It was light and described as north-south. One 
person in bed but awake said the bed rocked and a curtain swayed north-south, producing 
a sort of dizzy sensation. 

Fallon. — Three persons were found who claim to have been awakened; they were all | 
women and light sleepers. One (Mrs. EK. W. Black) awoke and heard a noise which she 
thought was the rattling of the window weights. Another (Mrs. I. H. Kent) awoke 
hearing a noise like the rattling of a window. She also noticed a bird cage and a hang- 
ing plant swing in a north-south direction, the distance from the point of suspension to 
the center of gravity of these being about 5 feet. Others in the same houses noticed 
nothing. 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 323 


It is reported that ditch tenders on the Government irrigation canal noticed a disturb- 
ance of the water surface, and light splashing of the water as if by low waves or rocking. 
They reported it at camp in the morning some hours before news of the California earth- 
quake arrived. Direct testimony is lacking on this point, tho the report was generally 
believed at the Reclamation Service Offices at Fallon and Hazen. 

Fairview. — Reports from several sources are to the effect that no shock was felt, and 
no distinct evidence of the earthquake was observed. 

Lovelock. — Several clocks are said to have stopt, but some of the reports, tho direct, 
seem to be unreliable. Several persons were awakened. One (Mr. Dawkins, principal 
of the Lovelock School) felt a slight shaking; others heard a noise as if a person were 
knocking, or the blinds or ventilators had rattled. One feared the powder house had 
“gone up.” (F. J. Gunnell, A. G. Bosk, C. H. Valentine.) The clock in the hotel is 
said to have stopt. It hangs on an east-west wall and faces south. The station clock, 
in a similar position, was also reported stopt. On several ranches 8 to 12 miles south of 
Lovelock the irrigators noticed waves or splashing in ditches or canals, and reported the 
same at breakfast that morning. Ditches extend north-south; the slope is very low, 
almost horizontal, and the water surface smooth and quiet. (John Sullivan, irrigator 
for Lovelock Commercial Co.; Peter Naker, rancher; James J ensen, son of rancher, etc.) 
One report speaks of a lamp swinging. Those who saw the effects on water surfaces, 
and others in general, felt no shock. 

Mill City. — The station agent said he had no positive indications of the earthquake 
and no one felt it. 

Unionville. —Tom Powell, a rancher 4 miles south of Unionville, says that his wife 
woke him about daylight, and called his attention to the lamp swinging. They felt no 
shaking. They noticed later that a fine dust from the adobe walls had crumbled down on 
to the surface of the cream. 

Winnemucca. — A rather thoro canvass of the town was made because it is the farthest 
east at which any report of the earthquake was made. Only one definite account was 
obtained, and it is believed to be reliable. Mrs. Sloane, nurse at the County Hospital, 
had been on night duty and had just retired. As she lay quietly in bed, she noticed a 
hanging lamp with pendant glass prisms swing. It swayed, in her judgment, nearly 3° 
inches, not far from east and west. She called her husband’s attention to it and suggested 
that it might be due to an earthquake. It continued swinging some time. No shock 
was felt, nor was swaying of the building noticed. The railroad agent, the weather 
bureau observer, who was up at the time, the postmaster, the employés in the telephone 
office, the people in both of the newspaper offices, and a number of other people in various 
parts of town, all said that they had felt no shock and had seen no effects of it, and knew 
of no one who had, except a few who had heard of the case of Mrs. Sloane. Another 
person, reported by one or two as having felt the shock, was interviewed, but claimed 
that she had felt. no shock and that the report must have been started as a joke. 

Hawthorne. — Two clocks are said to have stopt. Mrs. Taylor described the shock 
as a tremor, as if a pet dog were scratching and passing the bed, followed by a distinct 
movement toward the north and back toward the south. Mr. Brodigan, in the second 
story of the court-house, felt quite a shake. 

Mina. — The shock was distinctly felt by some. In the store it was said that the 
building distinctly swayed, the dishes and tinware on the shelves making some slight 
rattling. In the telegraph office the clock stopt. The shock was very slight, and felt by 
only a few. 

Bodie (i. B. Brooks). —The shock was perceptible; some clocks stopt. It was 
noticed by occupants in some 2-story buildings, but was not generally felt. 

Mono Lake. — A slight shock was felt on the west side of the lake. 


324 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION, 


Candelaria (Charles N. Platt, weather observer). — He did not feel the shock and knew 
nothing about it until the newspaper report came. 

Laws. — Ten or more persons noticed the shock, which was slight. W. M. Richards 
stated that there were 2 shocks, one almost immediately after the other. The first was 
a gentle rocking motion, the second small jerks. The total duration was about half a 
minute. 

Tonopah. — Several communications were to the effect that no one had noticed any 
indications of the earthquake. 

Goldfield. — Several reports were received to the effect that no shock was noticed. 
A report was in circulation that the springs had changed somewhat in their flow, but 
the Superintendent of the Western Reclamation Company (I. A. Thompson), who keeps 
a very close watch of the wells and springs, says there was no change at all in the flow 
nor any other indication of an earthquake. 

Eureka (Clay Simms).—A slight shock was felt, the movement being from west to east. 
It seemed to last for about a second. It made hanging objects swing, but did not stop 
clocks. 

Bishop (W. A. Chalfant). — The shock was strong enough to waken many persons 
asleep. Large clocks in the jewelers’ stores were stopt. The length of the vibration was 
unusual, but was not timed. The earthquake was not felt as a sharp shock, but rather as 
a long and not severe rolling motion. Doors, windows, window weights, etc., were 
shaken, and hanging objects, such as incandescent bulbs, swayed back and forth thru an 
are of 12 to 18 inches, double amplitude. No damage whatever was done to property. 
Doors on the north and south sides of buildings seemed to have been affected most. In 
one instance a box of dry goods was moved about 3 inches. Out-of-doors the rumble of 
the shock was noted by a few persons. 

Independence (Mrs. E. M. Brooks). —Some clocks were stopt and windows rattled, 
but few felt any shock. 

Lone Pine. — A number of clocks were stopt, all facing north or south. The shock 
was noticed by only a few persons. According to one description, there were 2 shocks a 
few seconds apart. It seemed like a rolling movement, and a hanging lamp was noticed 
swinging north-south. Trees shook. 

Keeler. — Only 2 or 8 persons noticed the shock. It was only slightly perceptible. 

In gathering information concerning the California earthquake of the morning of April 
18, as felt in the Western Névada region, two other closely succeeding shocks were brought 
to light, one of which had much stronger local effects than the greater but more distinct 
earthquake. 

The Earthquake of April 19, 1906, about 2" 5" p. M.: 

This shock was mentioned by so few persons that I was at first inclined to consider it 
imaginary. It was reported, however, by reliable persons not known to each other in 
three different towns. The most definite accounts are as follows: 

[eno (Miss Lewers). — Observer on the third floor of the Agricultural Building at the 
University, in the photographic laboratory; felt a very distinct shock, but did not re- 
member the direction of movement. 

Olinghouse (Miss Norris). —The person reporting and her sister were sitting in the house 
and felt a distinct shock. Fearing it was the forerunner of a larger earthquake, they ran 
outside. 

Hazen. — A shock not generally felt was noted distinctly by Mrs. MacGregor, at the 
Reclamation Service headquarters. 

The Harthquake of April 19, 1906, 8" 15" to 8" 30" p.m. (Intensity, IV-V.) — This 
earthquake was distinctly felt along the east slope of the Virginia range and the valley 
land directly east and not far north or south of Lat. 39° 31’. Wherever reported it was 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 320 


much stronger than the shake produced by the California earthquake of the previous day. 
It was generally felt at Hazen, Wadsworth, Olinghouse, and neighboring places where 
it is hard to find any one that noticed any effects of the great quake. In Hazen it rattled 
windows, made gas jets and lamps swing, and doors swing on hinges. The railroad 
station clock is said to have stopt. At Wadsworth, it made the windows rattle and eaused 
some fear, owing to reports of the San Francisco disaster. One person describes it as a 
quick sharp shock like a blast. At Olinghouse also it was felt as a sharp shock — one 
called it a quiver — and caused windows to rattle. It was felt as far east as Brown’s 
Station. It was apparently not felt at Fallon, tho it was distinctly felt 12 miles west at 
Carson Dam. In the Reclamation Service camp at Fernley it was quite strong, as felt 
on the ground in the tent. Judging from its areal distribution, it is suggested that this. 
earthquake is related to the fault along the east base of the Virginia Range. The rough 
time estimates vary from 8 to 9 o’clock, but in cases where the time was noted more par- 
ticularly, the variation is between 8" 15" and 8" 30". The vibration was apparently 
northwest-southeast, or north-south, at Hazen. At Fernley (a short distance south of 
Wadsworth) it was described as northeast-southwest. 


OBSERVATIONS OF J. A. REID. 


Professor J. A. Reid, who has been engaged for some time past in a geological study of 
the fault-zone of the eastern flank of the Sierra Nevada, made an examination of various 
faults with which he was familiar, with the view of ascertaining whether or not evidence 
could be found of movement at the time of the earthquake. No such evidence was, 
however, found. He also made an examination of several hot springs along the base of 
the mountains, to ascertain what changes, if any, had been caused by the shock. The 
only ones which seem to have been affected are the Steamboat Springs, 12 miles south of 
Reno. 

In addition to making these examinations, Professor Reid obtained some valuable 
information regarding the intensity of the shock, as given in his notes which follow: 

At Reno people were not generally awakened. There were no exact records of the time, 
direction, or intensity of the shock. The movement was large, but slow, and of long 
duration — probably about 40 seconds in total. The clock of ex-meteorological observer 
S. B. Doten stopt. An extension incandescent electric light, on an 8-foot cord, so ar- 
ranged that it could swing only north-south, was set swinging thru a 3-foot arc. This 
was on the first floor of an old wooden house, and gives some indication of the magnitude 
of motion and time of oscillation. Mr. Doten was awakened by the shock and counted 20 
seconds of lesser motion after he was fully conscious. No noise was heard. Another 
observer was awakened, and saw a 4-foot light and cord swing about 18 inches nearly 
east-northeast and west-southwest. At the University of Nevada similar lights were set 
swinging with a large east-west component of motion. 

At Steamboat Springs the shock was felt as a long, gentle swing. A second shock, 
seemingly as hard as the first, was felt the second or third night after. At the Rocky 
Hill Mine, in the foot-hills of the Virginia Range, midway between Steamboat Springs 
and Washoe, the shock was not felt by men at work, and loose rock in the main tunnel 
was not dislodged. 

At other points between Steamboat Springs and Carson, as at Lakeview, Washoe, and 
Lewer’s Ranch, the earthquake was felt as a long, gentle swing. At Bowers Mansion, 
a few feet from the steep granite escarpment of the Sierra Nevada, all sleepers were 
awakened by the shock, which appeared to have greater intensity near the harder, more 
elastic rocks than in the loose valley deposits. The same result occurred’in Carson 
Valley, south of Carson. At and near Genoa, directly at the base of the 4,000-foot scarp 
of the Sierra, the shock generally awoke sleepers, and trees were noticed to swing as in 


326 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


a wind. A few miles eastward, however, in the river-laid valley deposits, the shock 
was felt by very few persons. 

In the town of Gardnerville, some few miles east of Genoa, a number of people com- 
plained of a feeling of nausea while eating breakfast at the time of the earthquake, but 
felt no motion. In all cases the shock felt was characterized by long, gentle motion ; 
in no cases was sharp movement experienced. 

At Virginia City, about.6 miles east of the Rocky Hill mine, the shock was felt by very 
few people, and they were in the tops of the higher buildings. Around Dayton and 
nearby towns no reports came of persons feeling the earthquake. The Virginia Range 
seems not to have been greatly shaken. At Carson, the most reliable and abundant data 
were obtained. Mr. C. W. Friend, the well-known meteorological observer, obtained a 
seismograph record of the shock,’ which was by far the heaviest ever recorded by him, 
the stylus of the instrument swinging entirely off the plate. Yet the motion was so 
gentle and of such along period that sleepers were not generally awakened. The time 
of oscillation was not determined, but was described as being like the swinging of a ham- 
mock. The seismograph record is peculiar in that the stylus appears nearly to have 
retraced its course over one large curve. Carson lies about 3 miles east of the steep 
rise of the Sierra Nevada, with a deep deposit of river wash between. At the south- 
west, however, a low hill of schistose rocks just enters the town limits. This structure 
may play a considerable part in the peculiar motion of the earth here in this and other 
earthquakes. 

At Paradise Valley, north of Winnemucca, the earthquake was felt by the few people 
awake or moving at that early hour. A rancher who happened to be near a small pond 
noticed an unusual agitation of the water, and supposed an earthquake to be the cause. 
The time was subsequently found to correspond with that of the shock, as reported 
elsewhere. No motion was felt, however. 


. 


EXPERIMENTS WITH A SHAKING MACHINE. 


By F. J. Roasrs. 


The investigation described below was undertaken with the hope of offering some 
explanation, based directly on experiment, of the greater destructiveness of earthquakes 
in regions where the foundations of structures are supported by more or less soft ground 
than where these foundations are based on solid rock. 

As an earthquake consists in the actual shaking of the earth’s crust it would seem, 
upon first thought, that the more rigid the foundation the more destructive would be 
the effects of the earthquake upon the structures so supported. This is in general not 
true, however. 

In conversation with Dr. Branner, the great desirability of some experiments on this 
subject was suggested to the writer. In the first experiment which promised any inter- 
esting results a bucket of molding sand was poured out upon a board about 20 x 30 
inches. The board was shaken in a horizontal direction through an amplitude of 2 or 
3 centimeters, by means of a small motor. When the sand was moderately wet, the 
amplitude of vibration of the top of the mound was greater than the amplitude of vibra- 
tion of the board on which the sand rested. This result is contrary to what I should 
have expected. When the result of this preliminary experiment was reported to Dr. 
Branner some time afterwards, he was greatly interested and urged the writer to carry 
on a series of similar experiments on a larger scale, the same to form a part of the report 
of the Karthquake Investigation Commission. As a result the apparatus described 





.’ This seismogram is referred to in another part of the report. 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 327 


below was designed and was later constructed by the Mechanical Engineering Depart- 
ment of Stanford University. 

In designing a shaking apparatus to imitate an earthquake, certain conflicting con- 
ditions must be taken into consideration. It would seem that the apparatus ought to 
be on as large a scale as possible, but if it is on a large scale, it must needs be very expen- 
sive. If the linear dimensions are increased in any ratio, say trebled, the volume, 
weight, strength, and power to operate must be increased in the cube of this ratio; hence 
if the linear dimensions are trebled, these quantities must be increased 27-fold. ) More- 
over, it is obviously impossible, at any cost, even to approach the scale on which nature 
acts. With these considerations in view it was decided that the scale of the apparatus 
should be as small as is consistent with obtaining results from which general conclusions 
might be drawn. 

Earthquake motions are exceedingly complex, but it was not thought worth while 
to imitate this complexity, but rather to corfine the shaking motion to a simple to-and- 
fro horizontal motion in one direction. 


























Fic. 60. — Diagram of construction of apparatus used in experiments; 


A side elevation of the apparatus as finally constructed is shown in fig. 60. A is a 
direct current motor, B is a balance wheel weighing about 75 kg. The connecting rod, 
instead of being driven by an eccentric, is driven by an adjustable crank, H, which 
allows the stroke to be adjusted to any value up to 10 cm. Cis the car, whose internal 
dimensions are 100 x 86 x 30cm. The car is carried on steel rollers, D, D, 4 em. in 
diameter. The car, balance wheel, and motor were all mounted on a heavy framework 
securely bolted together. The drum G was mounted on an entirely independent sup- 
port. A paper wrapt around the drum received traces representing, (1) the motion of 
the car, (2) the motion of a block 1’ set in the material on the ear, and (3) the beats 
of an electromagnet J, electrically connected to a seconds pendulum. (The pencil 
actuated by the electromagnet was on the same side of the drum as the other tracing 
pencils, instead of being on the opposite side, as shown in the figure.) The block F was 
30 em. square and was furnished with side pieces running 6 cm. down into the sand, so 
that its motion was necessarily the same as the material immediately under and sur- 
rounding it. 

The experiment consisted in loading the car and then shaking it by means of the motor, 
with various amplitudes and frequencies. While the car was being shaken, the drum 
was rotated by hand, and the relative motion of the car and the block embedded in the 
load was determined by measuring the traces on the paper wrapt around the drum. 

The material with which the car was loaded was limited almost exclusively to ordi- 


s 


328 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


nary building sand from a creek bed, combined with various amounts of water. Some 
experiments were made with gravel, but lack of time and the necessity of completing 
the work for publication in the report of the Earthquake Investigation Commission 
prevented more extensive experiments. 

When the car was loaded with moderately dry sand containing 10 per cent of its weight 
of water or less, it was plain to direct observation that the sand was moving almost 
perfectly with the car, so long as the frequency was less than 2+ double vibrations per 
second. However, if the sand was wet locally by pouring water upon it, it was also 
very evident that the wet sand did not move at the same rate as the nearby dry sand. 
In the first place, the amplitude of vibration of the wet sand was greater than that of 
the dry sand; and in the second place, the reversal of motion was much quicker in the 
case of the former than of the latter. In the region between the wet and the dry sand, 
the difference in the relative motions of the two, causes the surface to be broken up by 
crevasses which open and close periodically. This breaking up of the surface is quite 
irregular, varying from moment to moment. 











Fig. 61. — Curves obtained on recording drum. Reduced about half. 


For a precise determination of the relative motion of the car and the sand with which 
it is loaded, it is necessary to measure the curves traced on the revolving drum described 
above. The method of doing this will be best illustrated by taking a particular case. 
Fig. 61 is a copy of one of the curves obtained on the drum. The lower sinuous curve 
is the trace made by the pencil attached to the car; the middle zigzag line is the trace 
made by the pencil attached to the block embedded in the sand; the upper line is the 
trace of the electromagnet beating seconds. In this particular case the sand contained 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 329 


all the water that it would hold, so that it was very soft, almost semi-fluid. The amount 
of water was determined by weighing a portion of the wet sand and then weighing it 
again after it had been thoroly dried. In this case the material contained 20 per cent 
of water to 80 per cent of sand. 

The traces show at a glance that the amplitude of the motion of the sand was much 
greater than that of the box. By reference to the transverse lines aa/ and bb’, it is ob- 
vious that the motion of the sand lags behind the motion of the box —in this case 
about one-sixth of a complete period. Finally, the difference in the character of the 
two motions is shown by the sine curve in one case, and the zigzag line in the other 
case. The sine curve shows that the car has a simple harmonic or pendulum motion, 
as must necessarily be the case on account of the way in which it is shaken. On the 
contrary, the block embedded in the sand moves with an approximately uniform velocity 
until the end of the “stroke,” when its motion is very quickly reversed; after which it 
again moves with uniform velocity until its motion is again quickly reversed. The 
acceleration at the instant the motion is reversed is a proper measure of the quickness 
of reversal. This acceleration can not be measured, but the average acceleration during 
a short interval of time while the motion is being reversed can be determined. If cd and 
cd’ (see fig. 6) are drawn at corresponding parts of the curves, then the lengths of these 
lines are proportional to the times required for corresponding changes in the two motions. 
The square of the ratio of these two times, divided into the ratio of the two amplitudes, 
gives the ratio of the two accelerations during the motion cPd. The closer cd is taken 
to P the greater this ratio becomes. In the present case, in which cd is drawn at one- 
tenth of the amplitude from P, the ratio of the two accelerations is about 3. As moving 
forces are always proportional to accelerations, the bearing of this result on the destruc- 
tiveness of earthquakes is evident. 

The data obtained from fig. 61 may be presented as follows: Load shaken, sand 80, 
water 20. Depth of sand, 22 centimeters. Frequency of motion, 1.7 double vibrations 
per second. Amplitude of car, 4.5 centimeters. Amplitude of block in sand 8.5 centi- 
meters. Lag of block, one-sixth period. Ratio of accelerations at reversal, 3 or greater. 

A large number of experiments were made with a load of wet sand having the above 
composition. Results similar to the above were obtained whenever the frequency of 
the motion was rather small. However, when the frequency of the motion was con- 
siderably increased, or when the ratio of water to sand was changed, the results obtained 
were quite different. In general the less water the sand contains the more nearly does 
it move with the car. The accompanying tables contain results from a large number 
of experiments in which the composition of the load and the frequency of motion was 
varied. 

The data from these tables are plotted in figs. 62 and 63. In all cases the number of 
complete or double vibrations per second is plotted along the z-axis, while the amplitude 
of motion of the block embedded in the sand is plotted along the y-axis. The points 
representing observations do not fall upon smooth curves, but this is hardly to be ex- 
pected from the nature of the experiment. 

The data as illustrated by the plots show that when the load consists of sand and water 
in the ratio 4 to 1, for low frequencies, the sand oscillates through a much greater ampli- 
tude than the car, and that the amplitude rapidly decreases as the frequency increases 
and becomes quite small for frequencies of 3 or 4 per second. On the contrary, when 
the load contains only 15 per cent of water, it moves with the car, for low frequencies, 
and the amplitude increases with the frequency. The results actually obtained are 
subject to a large probable error, but there can be no doubt about the decreasing ampli- 
tude with increasing frequency in one case and the opposite result in the other case. 
When the sand contains about 15 per cent of water, it seems to be more adhesive and 
more capable of packing into a relatively compact mass. In this respect it is distinguished 





330 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


Resulls of experiments in which composition of load and frequency of motion was varied. 
































































Water: SAND = 20:80 WATER: SAND= 17:83 Water: SAND = 15:85 
Amplitude in Centimeters Amplitude in Centimeters Amplitude in Centimeters 
Frequency Frequency Frequency 
Car Block Car Block Car Block 
15) Out 9.5 6 6.0 7.9 9 6.1 6.3 
MS 6.1 9.7 1.0 6.0 8.5 ied 6.2 7.4 
1.0 6.1 9.5 1.4 6.0 9.0 2.6 6.4 8.1 
lea 6.1 9.2 6 6.1 9.3 3.3 6.5 8.4 
Lb 6.1 ee 2:0 6.1 9.5 3.6 6.3 8.0 
7a 6.2 5.9 2.4 6.1 (a5) 
ae 6.3 1.9 2.8 6.1 8.0 1.0 3.2 3.4 
3:0 6.4 3 3.6 6.4 4.4 1.2 3.3 3.8 
3.8 6.4 4.3 1.8 3.3 4.4 
.83 4.3 7.4 2.7 3.4 4.7 
1.0 4.3 Wien .85 ous 5.2 3.2 3.4 Dek 
13 4.3 6.5 1.5 3.3 5.3 3.9 3.4 6.2 
PAA 4.3 3.5 2.5 3.3 5.4 4.0 3.4 5.0 
3.0 4.3 2.4 3.1 3.4 4.3 4.6 3.6 5.5 
4.0 4.5 1.2 4.1 3.0 2.2 










































































WATER: SAND = 12:88. La ihe = UN 4 t aces Dry GRAVEL. Wet GRAVEL. 
Amplitude in Cen- Amplitude in Cen- Amplitude in Cen- Amplitude in Cen- 
timeters B timeters timeters timeters 
Fre- Fre- 
Frequency quency quency 
Car Block Car Block Car Block Block 
1.8 6.2 6.3 1.4 4.4 4.5. 2.5 4.6 4.6 1.9 
2:5 6.4 6.4 2.0 4.7 6.3 2.8 4.6 4.9 20 
2.8 6.2 6.4 Bid 47 6.4 3.2 4.7 52 3.2 
3.2 6.7 7.0 2.5 4.7 6.5 3.3 4.8 5.4 3.4 
2.6 4.6 6.0 3.0 4.8 5.4 3.0 
1.0 3.1 3.1 2.6 4.8 5.5 San, 4.8 5.0 3.4 
1.8 3.2 3.2 3.2 4.7 3.8 3.8 4.9 5.2 3.4 
3.3 3.3 3.4 3.4 3.8 3.9 4.8 a5 
Bye) 3.4 Bsr 
4.0 3.4 3.8 
4.2 ane 3.8 





on the one hand from the soft and semi-fluid condition with a larger per cent of water, 
and on the other hand from a more friable condition with a smaller per cent of water. 
When the load contained only 12 per cent of water, the motion of the block embedded 
in the sand was very nearly the same as that of the car. For the data given, the motion 
of the block for the higher frequencies was slightly but unmistakably greater than the 
motion of the car. At another time, when there was about the same per cent of water 
in the sand, the motion of the sand was just as unmistakably less than that of the car, 
altho by only a small amount. In the latter case the sand was probably somewhat 
drier and less adhesive than in the former case. In still another experiment, in which 
the sand was very much drier, containing probably less than 5 per cent of water, the 
amplitude of the motion of the block was distinctly greater than that of the car, at least 
for frequencies of 3 per second. Of course this does not refer to the motion of the loose 
sand on top. The motion of a layer 1 or 2 em. deep of such loose, dry material was 
always much less than the motion of the car. 

In the above discussion we have been solely concerned with the motion of the block 
embedded in the sand in the middle of the car. The sand on the bottom and near the 
ends of the car has but little relative motion with respect to the car. A board thrust 
downward into the sand showed by its motion that the relative motion of the sand with 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. ool 


respect to the car increased from the bottom to the top. That the whole upper surface of 
sand in the car did not move together with the same speed was quite plain to direct 
observation. When the sand was very soft and wet, it rose and fell near the ends in the 
form of incipient waves, which, however, were not propagated away from the ends, three- 


6 a 
oe Sonat Wet gravel 
wy ee = Te QOLDry gravel 
So] ere 0 Ot car 


3 Tie 


D © 9° nN N 
fi | Pall 


oat 7wo /a yers 

wet ‘underneath 
N Car 
BA AGA Lue 


= 
N 


Amplitude of oselilation in centimeters 
d ® n 4h 
e ca tee 


\ $ 





Fig. 62.— Graphic representation of results. 


332 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


quarters of the surface remaining practically level during the vibration of the car. 
When the sand contained less water, the surface midway between the ends and the middle 
of the car was badly broken up by crevasses and ridges at right angles to the direction of 
motion. 

It doubtless frequently happens in river valleys, coastal plains, or “made land” that 
a very soft water-soaked subsoil is covered with a crust of more solid ground. This 
condition of affairs was imitated on a small scale. A lower layer 13 cm. thick of very 
wet sand containing 20 per cent of water was covered by a piece of oilcloth, and upon 
this was placed a layer 12 em. thick of much drier sand containing 10 per cent of water, 
and tamped into as compact a condition as possible. The block carrying the tracing 
pencil was embedded in this upper layer. If the whole load of sand had been like the 
top layer, it would have oscillated almost perfectly with the car. No such result was 
obtained with the two layers. When the car was shaken, it was apparent that there 
was still considerable freedom of motion in the lower layer. The upper layer moved as 
though it were floating on a semi-fluid mass. It rose and fell at the ends, and this 
motion extended to the middle, causing the block to rock back and forth, a result which 
was not obtained when the car contained a load of uniform consistency. The to-and- 
fro motion of the block was considerably greater than that of the car, for frequencies 
of 2 or 3 per second. For frequencies greater than 3, the amplitude of the block was 
less than that of the car. The results of this experiment are given in the tables on p. 330, 
while a plot of the same is included in fig. 62. The results, however, do not do justice to 
the possible destructiveness of such a motion. The rocking motion of the upper layer, 
as well as the violent manner in which it was broken up into fissures and ridges, seems 
to show that the destructive effect of the shaking motion of a semi-fluid mass may be 
increased when it is confined by a superincumbent layer of much more solid and com- 
pact material. 

In the last experiment with the shaking machine, the car was loaded with coarse gravel. 
The gravel consisted of water-worn pebbles of all sizes up to 2 inches in diameter. It 
contained no clay nor sand to bind the gravel together. When this load of dry gravel 
was shaken, the block embedded in the gravel moved with the same amplitude as the 
car until the frequency reached 3 double vibrations per second. With higher frequencies 
the amplitude of the block was somewhat greater. Considerable water was then poured 
into the ear, and it was‘again shaken with various frequencies. The results were similar 
to those obtained with the dry gravel, except that the relative motion of the gravel with 
respect to the car was nearly twice as great as in the case of the dry gravel. The data 
for these experiments are given in the table, while a plot of the same is given in fig. 62. 

A consideration of the meager and more or less erratic data described above suggests 
various questions and criticisms. It has already been explained why more extensive 
experiments involving other materials were not undertaken. The erratic nature of the 
experimental data is not due to the method of experimentation employed, but to the 
uncertain and varying condition of the material with which the car was loaded. If, in 
the beginning of a series of experiments, the composition of the load was thoroly uniform, 
this was no proof that it remained so. A few moments of shaking sufficed to change to 
a greater or less extent this uniformity. When the material contained a large percentage 
of water, continued shaking caused the material close up to the ends of the car to pack 
and become somewhat drier; this was also true, tho to a much less extent, of the middle 
portion. The portion midway between the ends and the middle, where the relative 
motion of contiguous portions of the load was the greatest (thus causing fissures and 
ridges to develop), noticeably increased its content of water. This development of non- 
uniformity in the consistency and composition of the load is a sufficient explanation of 
the irregularity of the results obtained. 


309 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 


‘o 


3 





Beli 
Y bh 





ey 


4. 








") 





PEF SECOND 


Number of complete oscillations 


Fic. 63.— Graphic representation of results 


304 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


With regard to the scale on which the experiment was performed, the question naturally 
occurs: Would similar results have been obtained if the car were very much largei ? 
One can not be certain, but it seems that such would have been the case if the frequency 
and amplitude of the car’s motion were the same. Several experiments were performed 
with a depth of 15 em. and 25 cm., and the results were substantially the same. The 
car was also divided by partitions running at right angles to the direction of motion, 
making a compartment of only half the length. The results tabulated below show that, 
at least in this case, the motion of the block embedded in the sand was not greatly affected 
by the presence of the partitions. 





Length of car between partitions in em. |101 49 101 101 49 49 101 
Frequency in double vibrations per sec. 2.2 2.25 2.3 2a 2.4 Dele 2.25 
Amplitude of carinem. . ... . 7.5 7.6 TH 7.6 7.5 7.5 7.5 
Amplitude of block in sandinem. . . NSS, 9.3 11.3 10.8 10.8 11.4 11.8 





In the experiment just described the material used contained 20 per cent water; with 
less water the partitions would doubtless have a greater effect in restricting the motion. 
It is also probable that with a larger car the relative motion of car and load would have 
been greater. 

Another question which is likely to oecur is: Does the solid or semi-fluid mass 
with which the car is loaded have a free period of its own which is comparable with the 
vibrations imprest upon it by the to-and-fro motion of the car? To elucidate this matter, 
the car was partially filled with water and the free period of gravitational waves deter- 
mined experimentally. The frequency of such waves was found to be 1.06. However, 
the load, instead of being like water, was in all cases exceedingly viscous and plastic. 
This condition would in any case decrease the natural vibration frequency of the load, 
and in the present case the viscosity was so great that the load could not possibly have 
any vibration independently of the oscillatory motion of the ear. 

Finally the question may be asked: What is the explanation of the fact that the load 
on the car (or the major part of it) oscillates thru a greater amplitude than the car which 
causes the motion? At present I have no comprehensive explanation of this fact. It 
undoubtedly depends upon the inertia of the load, combined with the greater or less 
freedom with which it yields to imprest forces. The load in the car is set into motion 
by two sets of forees: (1) On account of the motion of the bottom of the car a tangen- 
tial force is exerted on the bottom of the load and this is transmitted upwards by the 
rigidity of the load, or, exprest otherwise, by the mutual friction of successive layers of 
the load. (2) On aécount of the advancing motion of the end of the car the load re- 
ceives a thrust which is transmitted thru the material by its resistance to compression. 
Sometimes one of these sets of forces is of greater importance, and sometimes the other. 
One would be apt to think the end thrust was of the greater importance, but this is 
certainly not always the case, for when the load consists of a mound not resting against 
cither end of the car, the block embedded in the top of the mound may oscillate with 
a much greater amplitude than the car. (This was experimentally demonstrated.) In 
this case there can be no end thrust whatever. In some cases the end thrust may be 
more effective than the tangential force; this is probably the case when the frequency of 
motion is rather high. ) 

To those interested in seismology the important question is: How do these experi- 
ments help to explain the greater destructiveness of earthquakes in regions where foun- 
dations are in alluvial soil than where foundations rest directly upon rocky strata? To 
pass from experiments upon a box containing half a ton of soil to the destructive effects 
of an earthquake is certainly a great leap. In taking such a step, one is very likely to 
make mistakes. However, it seems to me beyond question that a soft, semi-fluid mass of 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 330 


soil, containing a large amount of water and surrounded or partially surrounded by solid 
strata, will not oscillate with the same motion as the surrounding strata. Moreover, 
in the case of the frequencies ordinarily occurring in earthquake motion, the amplitude 
of the oscillation of such a semi-fluid mass is likely to be greater than that of the sur- 
rounding solid strata; also the reversal of motion or the acceleration during reversal 
is likely to be greater than in the case of solid strata. Finally the greater relative motion 
of such a soft or semi-fluid mass is not prevented by overlying strata of drier and more 
compact material. 


REVIEW OF THE DISTRIBUTION OF APPARENT INTENSITY. 


In the preceding pages, all the data significant of the distribution of the intensity of 
the shock of April 18, 1906, have been set forth in such detail as seemed to be warranted 
in a statement of fact. The general conclusions drawn from the data are represented 
graphically upon the intensity map No. 23. It is proposed here, however, to call atten- 
tion to some of the more interesting and instructive phases of the distribution of inten- 
sity, and briefly to discuss their significance. 

It is to be noted, in the first place, that the region over which the disturbance was 
felt, extending from the Pacific Coast to Central Nevada, and from southern Oregon to 
southern California, is one of varied physiography. In a consideration of the relation 
of the physiographic features to the distribution of intensity, it will be necessary to 
distinguish only two classes of features; viz., (1) the mountain and hill slopes, generally 
underlain by firm rocks and veneered for the most part with a thin mantle of regolith 
and soil; and (2) the valley-bottoms usually underlain by a relatively great depth of 
infilled alluvium in a little coherent condition, and for the most part saturated with 
ground-water. 

The color bands on the map, indicating the gradation of intensity, show very con- 
siderable irregularities, or departures from the smooth curves which might reasonably 
be expected to obtain as the expression of such gradation of absorption of energy in 
homogeneous materials. To some extent such irregularities may be ascribed to the 
known lack of homogeneity in the firm elastic rocks of which the earth’s crust is chiefly 
composed. But the irregularities referred to are too great to permit us to regard such 
lack of homogeneity in the underlying elastic rocks as an important factor in determin- 
ing them. The irregularities are clearly related to the distribution of the valley lands. 


GENERAL DISPOSITION OF THE ISOSEISMALS. 


If now, before entering upon a consideration of these irregularities, we endeavor to 
ignore them, and so obtain a general conspectus of the color bands representing the 
gradation of intensity, the following features come out fairly clearly : 

1. On the northeast side of the fault-trace, the zones of equal gradation of intensity 
show a tendency to belly out to the northeastward, opposite the middle portion of the 
fault-trace. This tendency is most pronounced in the grades from VII to II of the 
Rossi-Forel scale, and is apparent in all grades below IX. 

The irregularities above referred to, associated with the distribution of valley lands, 
confuse somewhat the perception of this tendency, but do not detract from its reality. 

2. As a partial statement of the same general fact, the color zones become distinctly 
narrower, and their boundaries converge, as they approach the coast north of Eureka. 
This feature of the distribution of intensity clearly suggests that the isoseismal curves 
close in and swing around the end of the fault, and that there is, therefore, no indi- 
cation of a submarine prolongation of the fault beyond its known extent on the main- 
land in Humboldt County. 7 


336 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


3. The zones of equal gradation from IX to V of the scale are narrower at the southern 
end of the fault-trace than at the northern end, and they close around the end much 
more closely. This fact is suggestive of less depth of disturbance at the southern end 
of the fault. But the general disposition in the south of the zones ranging from V to 
II is not essentially dissimilar to those in the north. 

4, The disposition of the isoseismal curves along the coastal territory between Point 
Arena and Shelter Cove indicates that the trace of the fault on the sea-floor lies but a 
few miles off shore, and that its course partakes of the nature of a very obtuse sigmoid 
curve, approximately parallel to the trend of the coast. It follows from this inference 
that the fault observed in Humboldt County is continuous with that extending from 
the vicinity of Point Arena southeastward. No facts have come to light which weaken 
this conclusion, altho all the facts have been diligently sought for. 

5. On the southwest side of the fault, the territory upon which it has been possible 
to trace the isoseismals, particularly those ranging above VI, is very much smaller than 
on the northeast side. In so far as the territory available is representative of the entire 
southwestern crustal block, it appears, chiefly. from the isoseismals covering portions 
of San Mateo, Santa Cruz, San Benito, and Monterey Counties, that the intensity dimin- 
ished much more rapidly to the southwest than it did to the northeast. This interest- 
ing fact suggests that, of the two crustal blocks differentially displaced on the fault, the 
southwest block was perhaps the more passive. It may, however, indicate that the 
apparent intensity, as interpreted from effects on structures and objects, is a function 
of the character of the underlying rocks; since on the southwest side of the fault-trace 
there are extensive areas of highly elastic granitic rocks, while on the northeast side of 
the fault-trace these granitic rocks are deeply buried by sedimentary formations and 
appear nowhere at the surface west of the Sierra Nevada. 

6. The zones of equal gradation of intensity, ranging from X to VII, are fairly evenly 
spaced, tho broadening with diminishing intensity; from VII to VI the zone is notably 
broader, particularly in the northern portion of the region affected; and from VI to II 
the broadening of the zones is very marked. 


RELATION OF APPARENT INTENSITY TO VALLEYS. 


The generalizations above set forth are independent of the irregularities in the iso- 
seismal curves associated with the valleys. We may now inquire into the relationship 
which obtains betWeen the valleys and the distribution of apparent intensity. 

The most northerly locality where this relationship appears is on the flood plain of 
the Kel River, near the coast, in Humboldt County. The lower part of the Eel River 
Valley has been carved by stream erosion out of a synclinal trough of Pliocene strata 
having a thickness of over a mile. The syncline is flanked by older and much harder 
sandstones which are probably of Franciscan age. On the south of the valley these 
older sandstones constitute a bold mountain ridge, stept with terraces, which terminates 
in Cape Mendocino. The north side of the ridge has an east and west trend, and the 
Pliocene strata extend well up on its flanks. There is no suggestion of a fault on this 
side of the ridge, the trend being determined by the axis of the synclinal fold. The other 
side of the flood plain has a less regular northwest-southeast trend, converging upon 
the south side in the vicinity of Rio Dell. The flood plain is thus bounded by a wide 
trumpet-shaped but asymmetric contour terminating in lagoons and sand beaches south 
of Eureka. The depth of the alluvium of the flood plain is not known, but the features 
of the region suggest that it is undergoing subsidence and the alluvium may be several 
hundred feet thick. On this flood plain the apparent intensity was notably higher 
than on the surrounding slopes. This is shown by the extent of destruction in Fern- 
dale and other towns situated upon it, and by the rupturing and deformation of the 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 337 


alluvium of the flood plain itself, particularly in its lower part near the sea, and by the 
lesser destruction in the surrounding higher country. The data regarding the intensity 
on the high ridge to the south are scant, owing to the fewness of habitations, but on the 
Pliocene terrane on the northeast side of the flood plain, there was a distinct drop in 
the degree of destruction, altho this terrane consists largely of strata which are only 
partially indurated and but little coherent. 

The apparent intensity of the lower part of the Eel River flood plain grades from 
X to IX, tho in general nearer IX than X. It is surrounded by a belt of country where 
the intensity grades from IX to VIII. This belt has a width of a few miles on the Plio- 
cene terrane to the northeast of the flood plain, and probably scarcely extends to the 
harder Franciscan rocks of the ridge to the south. The facts thus necessitate the recog- 
nition on the intensity map of an area of high intensity, including a range from X to 
VIII, in the midst of a region where the prevailing intensity ranges only from VIII to 
VII. This, as will be seen in what follows, is typical of all the more important alluviated 
valleys of the Coast Ranges, and indicates clearly that the apparent intensity for such 
situations is a function of the underlying formations. 

On the more limited flood plain of the Mattole River at Petrolia, the destructive effects 
were even more intense than at Ferndale, and in marked contrast to those apparent in 
the few scattered houses on the rocky upland. But little can be inferred from this con- 
trast, since Petrolia is situated on the projection of the fault-trace, and only a few miles 
~ beyond the most northerly point to which it has been mapped. 

The town of Willets is at the headwaters of a branch of the Eel River on a flat allu- 
viated valley-bottom several miles in extent. The situation and character of the valley 
are such as to suggest that it is a filled-in lake basin. The ground-water below the 
valley-floor stands within a few feet of the surface. The town is 26 miles from the 
coast at Mendocino City, and not less than 30 miles from the fault-trace; yet the ap- 
parent intensity was not less than IX of the scale, or equal to that which prevails on 
the hard rocks in the zone, the distal border of which is usually not more than 6 miles 
from the fault-trace and often much less. Between Willets and the coast the intensity 
had diminished from X in the vicinity of the fault-trace to less than VII. This rapid 
rise from less than VII in the territory immediately to the west, to IX on the valley- 
floor, with no evidence of other factors intervening, and no evidence of similarly high 
intensity on the rocky slopes surrounding the valley, again indicates that the apparent 
intensity is a function of the character of the valley-floor. 

A similar condition prevails in the valley in which Ukiah is situated, 20 miles to the 
south of Ukiah. The physiographic features of the valley are described by Mr. George 
McGowan in his report describing the effects of the earthquake at Ukiah. The town is 
about 27 miles from the fault-trace, and in this interval the intensity had diminished 
from X to less than VII. In Ukiah, which is on the old flood plain of the Russian River, 
near the middle of the valley-floor, the intensity rose to between IX and VIII. Here 
again, there can be little doubt as to the influence of the underlying formations upon the 
destructive effects of the shock. This conclusion is supported by the time at which 
the shock was felt. Ukiah is one of the few places where satisfactory time observations 
were obtained. 

At the International Latitude Observatory, Dr. Townley reports that he was 
awakened by the shock and lookt at his watch, finding the time (corrected) to be 
5" 12" 30°, and he is of the opinion that the shock commenced at 5" 12" 17°. This 
accords fairly well with the time the shock was due at Ukiah, and affords no suggestion 
that the local high apparent intensity may have been due to a local earthquake. 

Another valley area of high intensity is on the west side of Clear Lake, extending 
from Kelseyville to Upper Lake. Lakeport, in the central portion of this area is 36 

Z 


338 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


miles distant from the fault, with 2 mountain crests intervening. In this interval the 
intensity had diminished from X to less than VII, but at Lakeport and Upper Lake it 
rose to IX. The topographical and geological maps of the Clear Lake district, published 
by Becker,’ show that Lakeport and Kelseyville are on an alluvial plain, the under- 
lying deposits of which are of Quaternary age; and the same conditions prevail at Upper 
Lake. Between this area of alluvium and Bartlett Springs, on rocky ground, 10 miles 
to the east of Upper Lake, the intensity dropt to VI. At Lower Lake, situated on 
Tejon sandstone, the intensity had similarly dropt to VI; and these intensities are about 
the normal for the distances at which Bartlett Springs and Kelseyville lie from the fault 
along the coast. At Highland Springs, the intensity was between VII and VI, which 
is also about the normal for its distance from the fault. It thus appears that the high 
apparent intensity was confined to the alluvial or recent lake deposits of the area about 
Lakeport. These facts indicate that the high apparent intensity for this area was prob- 
ably not due to a local earthquake, coincident or nearly so with the main shock, but 
that the destructive action of the latter was locally augmented by conditions inherent 
in the underlying incoherent deposits. For if there had been a local dislocation, its 
effects would undoubtedly have made themselves manifest over a wider area than that 
occupied by these deposits. The character of the shock, as described by those who 
experienced it in the vicinity of Clear Lake, agrees, moreover, with that of the shock 
emanating from the fault at the coast. Becker’s geological map of the district shows 
no faults traversing it. 

In general, then, while from the nature of the case it is not possible to deny positively 
that a local earthquake may have occurred on the morning of April 18, 1906, at the same 
time as the main shock, no evidence appears to sustain that view. On the other hand 
the evidence here as elsewhere supports the belief that the apparent intensity is a func- 
tion of the underlying formations to the extent manifested in this district. 

Coming now to Santa Rosa Valley, we encounter an interesting case of high intensity, 
associated with an alluvial valley-bottom. The valley may be described as an oval- 
shaped area, extending for 24 miles from Healdsburg to the vicinity of Penn’s Grove, 
with a maximum width of 8 miles on a line lying between Santa Rosa and Sebastopol. 
The general trend of the central axis of the valley is about N. 30° W. It is thus not 
far from parallel with the general trend of the fault along the coast. Over a considerable 
expanse the valley-floor is perfectly even, and appears level to the eye. At its widest 
portion, however, it has a slope from an elevation of 170 feet above sea-level in the eastern 
part of the city of Santa Rosa, to about 50 feet above sea-level, a descent of 15 feet to the 
mile. In this section there are no terraces, but a perfectly even profile. To the north of 
Santa Rosa, however, the floor of the valley is less even, and it is stept in a few broad 
terraces, the lowest of which is the present flood plain of the Russian River. 

The geomorphogeny of the valley is not altogether simple; the primary fact in its 
development, however, is that it has been carved by stream erosion to its full width out 
of a great syncline of Merced (late Pliocene) strata.? The upturned edges of these Merced 
strata, planed down to an even but now somewhat dissected surface, constitute the floor 
of the upper terrace lying to the north of Mark West Creek at an altitude of about 200 
feet above the flood plain of the Russian River. On a somewhat lower terrace is the town 
of Windsor. South of Mark West Creek, the valley is in general deeply alluviated and the 
wells a little to the east of the city of Santa Rosa (150 feet deep) show that the alluvium 
is saturated with ground-water to within a short distance of the surface. The distribu- 
tion of this ground-water thruout the valley is, however, not well known, no systematic 
investigation ever having been made. On the western side of the valley from Sebastopol 





* U.S. Geological Survey, Monograph XIII. 
> Cf. Osmont, Bull. Dept. Geol., Univ. Cal., vol. 4, No. 3. 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 339 


northward to Mark West Creek, the drainage is stagnant and gives rise to the Laguna de 
Santa Rosa. This lagoon is a drowned water course in free connection with the trunk 
drainage of the Russian River, and is indicative of a deformation of the valley surface 
whereby the western side has been deprest below the base-level established by the Russian 
River. From these statements it will be apparent that the whole of the floor of the Santa 
Rosa Valley is not alluviated, but that portions of it — particularly that portion lying 
between Mark West Creek and Healdsburg and east of the flood plain of the Russian 
River — is a terraced platform carved out of the Merced terrane. 

Now the notably high apparent intensity of the earthquake shock was confined to the 
alluviated portion of the valley-floor. The 2 centers of population which suffered most 
severely were Santa Rosa and Sebastopol. At Windsor, situated on the terrace cut in 
the Merced rocks, the intensity was distinctly lower. Healdsburg, at the northern extrem- 
ity of the valley, is also on alluvium and the intensity was here again high, tho not quite 
equal to that at Santa Rosa and Sebastopol. The town of Guerneville, on the old flood 
plain of the Russian River, below the Santa Rosa Valley, suffered most severely; while 
the cemetery of the town, but a short distance away, on a rocky terrace 190 feet above 
the town, was affected in a distinctly less degree, only one monument having been over- 
thrown, and a few moved on their pedestals. The rapid diminution of intensity on pass- 
ing from the alluvium to the rocky slopes, thus specifically illustrated at Guerneville, is 
characteristic of the borders of the Santa Rosa Valley. To the east of the city of Santa 
Rosa, this diminution is so rapid that the gradation of intensity can not be adequately 
exprest upon the intensity map. Under these circumstances it is difficult to avoid the 
conclusion that the severity of the earthquake shock on the alluvium of the Santa Rosa 
Valley is in large measure referable to the character of the ground. Were a local shock 
a factor in the case, we should expect that the high intensity would not be limited to the 
alluviated area, but would also be manifested on the surrounding mountain slopes. This 
expectation not being realized, the hypothesis of an independent local shock stands with- 
out support. ‘The general position of the isoseismal curves off the valley-bottoms is not 
notably affected by the high apparent intensity in the valleys. In arriving at the con- 
clusion that the high apparent intensity in this valley is referable in large measure to the 
character of the ground, it is not thereby intended to exclude other contributory factors. 
A theoretical discussion of the effect at the surface of the earth of a concussion at a point 
within the crust shows that for a certain path of emergence the horizontal jerk of the 
emerging earth-wave, and, therefore, the destructive effect in general, would be at a max- 
imum. The fact that the earthquake under consideration was due not to a concussion at 
a point, but to a jar developed by movement on a plane at least 270 miles long, reaching 
to the surface and of unknown depth, renders the application of this doctrine difficult 
and of questionable value. Nevertheless, the tendency, which is demonstrable in the 
ideal case, would also exist in the more complex actuality; and it is by no means impos- 
sible that the zone of maximum destruction may fall in a general way within the Santa 
Rosa Valley, and would thus be a factor conducive to excessive destruction, in addition 
to the factor inherent in the character of the ground. This suggestion, to have weight, 
should be corroborated by observations in other portions of the general zone of destructive 
effects, and it must be confest that satisfactory corroboration is lacking. 

While the geology of the Santa Rosa Valley has not been mapped in detail, owing to the 
lack of topographic maps, it has been carefully studied, particularly from the structural 
and stratigraphic point of view, by Mr. Vance Osmont,! and no fault traversing the valley 
was found by him. The underlying structure, so far as has been made out, is as already 
stated that of a broad, rather simple, synclinal fold. It has also been indicated that the 
surface of the valley has been subjected to recent deformation, whereby the western side 


? Bull. Dept. Geol., Univ. Cal., vol. 4, No. 3. 








340 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


has been deprest: below the local base-level. This may be taken as an indication of the 
persistence of the compressive forces which originally gave rise to the syncline. If, now 
the underlying rocks of the valley were in a state of synclinal stress, the relief of that stress 
afforded by the dislocation along the line of the Rift might give rise to an elastic dis- 
turbance of the ground which would be additive to the shock generated at the fault along 
the Rift. 

But none of these suggestions, whether of contributory shock, or an unrevealed fault, 
or of coincidence of the valley with a vaguely defined zone of maximum horizontal 
jerk, or of sudden relief from synclinal compression, are sustained by satisfactory evidence. 
They are possibilities which, with the facts before us, it is possible neither to affirm nor 
to deny. The reference to them in this place is only excusable on the ground that they 
are suggestive of lines of inquiry which may perhaps be profitably undertaken at some 
future time. On the other hand, the influence of the character of the ground upon the 
apparent intensity is sustained by cumulative evidence. 

In Sonoma and Napa Valleys, the disposition of the isoseismals is very evidently de- 
termined by the contour of the valleys, the high intensities running far up the valleys 
within areas of lower intensity on either side. In Sonoma Valley the upper and lower 
parts are alluviated, while the middle part is not; or, if so, only to a slight extent, and it 
is being trenched by the stream which flows thru it. The floor of Napa Valley, on the 
other hand, is alluviated thruout, save for some rocky spurs and isolated rocky hills which 
occur along portions of the sides of the valley. The intensity diminishes in the upper part 
of Napa Valley, in the vicinity of Calistoga, where the alluvial deposits thin out, notwith- 
standing the fact that Calistoga is somewhat nearer the fault along the Rift than is 
Napa City, at the lower end of the valley, and notwithstanding the fact that Calistoga is 
approximately on the line of the Mount St. Helena fault described by Osmont. If the 
relatively high apparent intensity of Napa Valley were in any way referable to a local 
earthquake on a fault traversing the valley, we should not only expect the effects to be 
manifested on the rocky slopes of the valley, as well as upon its floor, but would also expect 
higher intensities on the line of the only well-defined fault known to traverse the valley. 
Neither of these expectations is realized, and upon the slopes of Mount St. Helena, in the 
vicinity of the fault which traverses its western front, the intensity was notably low —not 
higher than VI. We are thus again forced to fall back upon the character of the ground 
as the immediate cause of the high apparent intensity on the alluviated valley-floor, 
particularly in the lower part of the valley. 

Specific and instructive instances of the influence of the character of the ground upon 
the apparent intensity of the shock are afforded by the cities of Petaluma and San Rafael. 
Each of these cities is built partly upon rock and partly upon the alluvium of the tidal 
marshes of the San Francisco Bay. Petaluma is situated at a distance of 14 miles from 
the fault, and San Rafael at a distance of 9 miles. In both cities the damage to buildings, 
chimneys, etc., was notably less upon the rock than upon the alluvium, altho the latter 
can not in either case be supposed to have any great thickness at the base of the hills. 
(See fig. 64.) 

In the city of San Francisco the detailed study of the distribution of intensity, so suc- 
cessfully carried out by Mr. H. O. Wood, affords a conclusive proof of the paramount 
influence of the character of the ground in determining the high apparent intensities 
which affected portions of the city. On the made land in the vicinity of the Ferry 
Building, about 9.5 miles from the fault, as well as on the tidal marsh jand, and along 
Mission Creek and Lagoon, between 7 and 9 miles from the fault, the intensity was X of 
the Rossi-Forel scale. But on the rocky top of Telegraph Hill, near the ferries, the in- 
tensity was scarcely higher than VII. On the sandstone cliffs at Point Lobos, about 3 
miles from the fault, it was about VIII; and on the summits of the chert hills in the cen- 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 041 


tral part of the city and county of San Francisco, 5 to 6 miles from the fault, it was 
about VII. On the alluvium of Mission Valley, at distances of from 6 to 9 miles from the 
fault, the intensity varied from less than VII to between VIII and IX. 

Under similar conditions of ground, the shock was greater nearer the fault; but there 
was much greater contrast between the damage produced by the shock on the summit of 
Telegraph Hill and that in the vicinity of the Ferry Building, at like distances from the 
fault, than there was between the damage near the ferries and that in the immediate 


























Fic. 64. — Distribution of intensity in Petaluma. Vertical lines represent area of low 
alluvial land, on which nearly all chimneys were damaged. Horizontal lines rep- 
resent Slopes underlain by rock, on which about half the chimneys were damaged. 
The solid black areas and dots represent exceptionally severe damage. The blank 
area inclosed by dotted lines represents a belt of practically no damage. By R. 58. 
Holway. 


vicinity of the fault. Thus, notwithstanding the general tendency of the intensity 
to diminish with increasing distance from the fault, it seems to be unquestionable that 
the degree of intensity which prevailed at any locality in the city depended chiefly on 
whether the underlying formations are firm rock or incoherent material more or less 
saturated with water. It would even seem possible to discriminate slight differences 
of apparent intensity on different kinds of firm rock for the same distance from the fault. 
Thus the chert hills appear to have suffered less disturbance that those where serpentine 


342 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


outcrops; and the sandstone areas were more disturbed than the serpentine. But these 
differences are minute. 

In the case of the made land and old marsh land of San Francisco, where the apparent 
intensity reached X, there can be no question as to possible local shocks, since the exces- 
sive disturbance was so strictly limited to the area lying outside of the original shore line 
and marsh border. 

In the low ground about San Francisco Bay to the south of the city, we have another 
instance, on a rather large scale, of high apparent intensity determined by the incoherent 
water-saturated condition of the underlying formations. San Francisco Bay in general, 
and the southern portion of it in particular, lies in an alluviated valley which has been 
deprest so that its central portion is now below sea-level. This submerged valley-floor 
passes insensibly into the Santa Clara Valley which encloses it on the south and extends 
southward between the Santa Cruz and Mount Hamilton ranges. Treating San Fran- 
cisco Bay and Santa Clara Valley as one physiographic feature, it may be stated, without 
going into the evidence in detail, that depression and alluviation have both been greater 
in the southern end than in the northern. This southern portion of the valley con- 
stitutes a great artesian basin, and many wells have been sunk in it. The deprest trough 
is not, however, wholly filled by alluvium, since several wells have past through late 
Quaternary strata containing marine fossil remains. It would appear, from the sections 
revealed by these wells, that with the progress of subsidence, marine deposition alternated 
with alluviation. The deposits, whether marine or alluvial, appear to be incoherent 
or unconsolidated, consisting of clays, sands, and gravels, in layers of irregular thick- 
ness and extent. Many wells have past through several hundred feet of such materials 
without reaching bedrock. One well, on the edge of the marsh near Alvarado, reached 
rock at a depth of 730 feet. At the sugar-mill at Alvarado, and at the Contra Costa 
pumping plant, in the same vicinity, there are several wells from 300 to 400 feet deep, 
passing thru clay, sand, and gravel without reaching bedrock. At Roberts’ Land- 
ing-there are 2 wells, one 574 feet deep and the other 540 feet deep, which past thru 
alternations of clay, sand, and gravel, but did not reach bedrock. A well 1.5 miles 
south of Milpitas past thru 11 layers of gravel aggregating 166 feet and 12 layers of 
clay aggregating 218 feet — total depth 384 feet — but did not reach bedrock. The 
wells in the vicinity of San Jose range in depth from 35 to 500 feet as a rule. One well 
on the bank of Guadaloupe Creek, however, was sunk to a depth of 1,100 feet, but did 
not penetrate bedrock. A well at Stanford University is in gravel at 412 feet. On the 
west side of the Bay there are several hundred wells, most of them less than 100 feet in 
depth, while the deep ones are usually a little more than 300 feet. Wells are even bored 
in the bottom of the Bay and an abundant supply of fresh water is obtained from them. 
These brief statements will be sufficient to afford a general idea of the extent to which 
the valley has been deprest and filled in with deposits as yet unconsolidated. To the 
south, the rocky floor of the valley appears at the surface in the vicinity of Coyote, 12 
miles south of San Jose. Beyond this, however, the valley again opens out and is 
deeply alluviated. 

On the floor of this valley, from San Bruno Mountain southward, on both sides of the 
Bay, and southward a few miles beyond San Jose, the intensity was abnormally high. 
On the rocky slopes between the western edge of the valley-floor and the fault, the 
intensity had dropt from X at the fault to VIII at the base of the hills. On the valley- 
bottom it again sharply rose to IX. On this ground were Stanford University, Red- 
wood City, San Mateo, the 44-inch pipe of the Spring Valley Water Company, San Jose, 
Agnews, Milpitas, and Alvarado. On the eastern side of the Bay the intensity of LX 
did not persist to the base of the hills, but extended only about halfway from the shore 
line to the edge of the valley. There was therefore a distinctly diminishing intensity in 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY, | 343 


approaching the base of the hills on this side of the valley. But at the base of these hills 
lies one of the dominant faults of the country — the fault upon which movement took 
place, with rupture of the ground, producing the earthquake of 1868. It would seem 
that, if local earthquakes were to be invoked to explain the high intensity of the alluviated 
valley-bottoms, here was a fine opportunity for an illustration of that doctrine. But the 
seat of the disturbance of 1868 was perfectly passive in 1906. The intensity diminished 
eastward right up to the fault-trace; and there is no suggestion that the disturbance 
along the San Andreas Rift affected it in the slightest degree. This being the case, 
there appears to be no recourse but to ascribe the normal apparent intensity about 
the southern part of San Francisco Bay to the character of the underlying formations 
as in other valleys before described. 

To the west of the San Andreas fault in San Mateo and Santa Cruz Counties, the 
apparent intensity diminishes on the firm rocks more rapidly than to the east of the fault, 
but it rises very notably on the alluvial fan of Pilarcitos Creek at Half Moon Bay, and 
in the alluviated valleys of San Gregorio and Pescadero Creeks, Going westward 
down Pilarcitos Canyon, the apparent intensity drops from X at the fault to less 
than VII within 4 miles of the fault; but along the coastal fringes of alluvium which lie 
between the hills and the sea, it rises again to VIIT at Spanish Town and to IX on the 
flats below the town. In the valleys of San Gregorio and Pescadero Creeks an apparent 
intensity of from VII to VIII extends for 4 miles and 3 miles, respectively, into an area 
of hill lands where the prevailing intensity is from VI to VII. The geology of this 
region, the Santa Cruz Quadrangle, has been mapped by Prof. J.C. Branner, and no fault 
is known at Half Moon Bay. Farther south the San Gregorio fault crosses the mouth of 
San Gregorio Valley and the middle part of Pescadero Valley, with a course parallel to 
the trend of the coast or transverse to the axes of the valleys. But the high apparent 
intensity in the bottoms of these valleys can not be referred to a local earthquake due 
to movement on this fault, since on either side of both valleys, in the immediate vicinity 
of the fault, it drops to below VII; while a few miles farther south on the same fault the 
apparent intensity drops to VI. 

At Santa Cruz a portion of the city is built partly on a series of broad wave-cut terraces 
in the bituminous shale of. the Monterey series and partly on the alluviated bottom- 
lands of San Lorenzo River. The contrast in apparent intensity in these two portions 
of the city is marked. In that portion which is situated upon the terraces the apparent 
intensity ranges from VII to VIII, while on the bottom-lands of the river it rises to 
from VIII to IX. It thus appears again, from a consideration of these four cases on the 
coast extending from Half Moon Bay to Santa Cruz, that the character of the material 
in the alluviated valley-bottoms has exercised a dominant influence in determining the 
apparent intensity of the earthquake shock, and that there is nothing in the facts to 
suggest that any other factor has played an important role. 

The finest illustration of the influence exercised by alluvium in the production of 
high apparent intensity is that afforded by the valley of the Salinas River and its exten- 
sion to the valley of the lower portion of the Pajaro River. The Salinas Valley is one 
of the notable physiographic features of the Coast Ranges. It lies between the Santa 
Lucia and Gavilan Ranges. It is deeply alluviated and strikingly terraced, particularly 
in its lower part. The course of the valley was probably determined originally by the 
fault along the eastern base of the Santa Lucia Range. The river discharges into the’ 
Bay of Monterey about its middle part, a few miles south of the mouth of the Pajaro 
River. On the flood-plain tracts of both rivers, and along the beach of the Bay of Mon- 
terey, the intensity was 1X. This extended up the river for several miles above the town 
of Salinas. There were extensive fissures in the alluvium as far as Gonzales, with slump- 
ing of the ground toward the river trench. Damage of structures, indicating an intensity 


o44 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


of VIII, extended up the valley as far as Chualar; and the limit of intensity, VI, was 
reached only at King City, 45 miles above Salinas; VI in the vicinity of San Ardo, 65 
miles; and V at Pass Robles, 99 miles above the same point. The isoseismals drawn 
thru these points are almost parallel to the river, the intensity to the east and west 
diminishing rapidly. The town of Salinas is about 13 miles distant from San Juan, 
in a direction normal to the fault-trace. On the northern end of the Gavilan Range, 
which intervenes between the two valleys, the apparent intensity dropt to V and then 
rose rapidly to [X in the Salinas Valley. The limitation of the high apparent intensity to 
the valley-floor, the practically symmetrical parallelism of the isoseismals to the median 
line of the valley, and the diminution of the intensity with the thinning of the alluvium 
and the constriction of the valley upstream, all indicate dependence of the character of 
the shock upon the constitution of the underlying formations, and suggest no other 
factor. 

Still farther south in San Luis Obispo and Santa Barbara Counties, far beyond the 
isoseismal IV, an apparent intensity of IV is indicated by the effects observed in the 
valley-lands at San Luis Obispo, Edna, Arroyo Grande, Pismo, Santa Maria, Casmalia, 
and Lompoc. In the flat alluviated valley-bottom in which the town of Hollister is 
situated, about 8 miles east of the southern end of the fault at San Juan, the apparent 
intensity rose to IX, but diminished very rapidly on the hill lands immediately to the 
east of the valley to VI, which appears to have been the normal intensity for the moun- 
tainous tract between Hollister and the San Joaquin Valley. 

Farther southeast there was a similar but less marked rise in the apparent intensity 
at Lonoak, Priest Valley, and Hernandez, all of these being on alluviated bottoms. 

In the alluviated valleys to the east of the Berkeley Hills, the apparent intensity was 
abnormally high and the area occupied by these valleys constitutes an isolated area in 
which the intensity ranges from VII to VIII in the midst of a belt in which the range 
is from VI to VII. At Pleasanton the intensity was somewhat higher than at Sunol, 
altho the latter is nearer the fault of April 18, 1906, and is situated, moreover, on the 
line of an old fault which traverses the west side of Livermore Valley and extends up 
Calaveras Valley into the Mount Hamilton Range. At Livermore, in the more open 
part of the valley, where the alluvium is deeper, tho 8.5 miles farther from the seat 
of disturbance, the intensity was about the same as at Sunol. At Martinez, on an 
alluviated embayment of Suisun Bay, the damage due to the shock was much greater 
than in neighboring towns situated on rock, even when the latter were nearer the fault. 
Beyond Martinez to the eastward there is a very marked bulge to the east of Suisun 
Bay, in the isoseismal VII, which can be attributed only to the low and marshy character 
of the ground. The apparent intensity at Antioch was a degree higher in the seale than 
that at Mount Hamilton, altho it is double the distance from the fault of April 18; and 
altho there are several old faults in the vicinity of Mount Hamilton and none are known 
near Antioch. 

The influence of the valley-lands upon the apparent intensity is well shown on a large 
scale in the disposition of the isoseismal curves about the Sacramento Valley. In the 
mountains to the west of the Sacramento Valley the apparent intensity ranges in gen- 
eral from VI to V; but on the floor of the valley eastward to beyond the Sacramento 
River, it is very uniformly about VI or VI+. 

The most interesting case of high apparent intensity in a valley-bottom remote from 
the San Andreas fault is that of the San Joaquin Valley. This case merits especial 
consideration, since of all the valleys here considered it is the one which is most sug- 
gestive of the occurrence of a local earthquake, distant from, tho connected with, 
the main movement on the San Andreas fault. While the suggestion is strong, however, 
the eyidence is not conclusive of the occurrence in this region of a quasi-independent 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 345 


earthquake; and all that can be done is to indicate the evidence which points that way, 
and cite certain facts which detract from the force of that evidence and tend to corre- 
late the locally high intensity in the San Joaquin Valley with similar high apparent 
intensities in other valleys thus far discust. 

The apparent intensity on the floor of the Sacramento Valley, as has been stated, 
ranges about VI + of the scale. This is somewhat higher than at several points in the 
adjacent Coast Ranges to the west, and the difference is ascribable to the alluviated 
character of the valley-floor and the water-saturated condition of the alluvium. As we 
follow the Sacramento Valley southward into the San Joaquin Valley, it converges upon 
the San Andreas Rift, and we should naturally expect an increase in the intensity by 
reason of the diminution of the distance from the seat of disturbance. This expecta- 
tion is in a measure realized by an eastward bulge in the isoseismal VII opposite Suisun 
Bay, and by the somewhat higher intensity at Tracy and Westley than at Sacramento 
and Stockton. 

Southward from Westley, however, the apparent intensity increases at a rate which 
can not be referred to the slight approximation of the region to the seat of the main 
disturbance. At Crow’s Landing the apparent intensity is VII; at Newman it is VEE: 
at Volta it is VIII+; and at Los Banos it is IX. These points lie on the west side of 
the valley between the San Joaquin River and the flanks of the Coast Ranges. South 
of Los Banos, on the valley floor, settlements are very few, and information as to the 
apparent intensity is unfortunately lacking over an extensive territory. At Coalinga, 
however, the apparent intensity is VII, indicating that the abnormally high figures 
prevail over the western side of the valley from Crow’s Landing to southward of Coalinga, 
a distance in a north and south direction of not less than 100 miles. That the high 
apparent intensity was not wholly confined to the valley-floor, but also extended into 
the flanks of the Coast Ranges, is shown by the remarkable series of landslides which 
were started by the earthquake for a distance of about 23 miles northwestward from 
the vicinity of Cantua, reported by Mr. §. C. Lillis, and described by Prof. G. D. Louder- 
hack in another part of this report. 

\Now Los Banos, where the apparent intensity was highest, is distant 40 miles from 
tht nearest point on the San Andreas fault at San Juan, its southern end. It is nearly 
34 ‘niles in an air-line from Hollister, the nearest point to the westward having a simi- 
larly high apparent intensity. In the Coast Ranges between Hollister and Los Banos, 
the intensity was as low as V. 

Thise facts are suggestive, as already stated, of a local disturbance at or about the 
se Hn as the main movement along the San Andreas fault. 

Certain circumstances detract, however, from the force of this suggestion, and indicate 
another'possible explanation which, it must be confest, is not very conclusive in view of 
the remcteness of Los Banos from the seat of disturbance. The portion of the San 
Joaquin Valley in which Los Banos lies is undoubtedly an underground water reservoir. 
It lies at the base of the alluvial fans of the Coast Ranges where the streams sink, and 
the waters \f the San Joaquin River maintain the water-table at no great distance below 
the surface.\ As shown by the experiments of Prof. F. J. Rogers, described in another 
part of this teport, water plays an important part under certain conditions in increasing 
the amplituds of the earth vibrations and, therefore, their destructive effect. In this 
respect the region about Los Banos would be particularly favorably conditioned for the 
development & high apparent intensities, as inferred from destructive effects. The 
general conditioys are quite analogous to those in the Salinas Valley, in the bottom-lands 
of the Pajaro River and the Russian River, and in the region about the south end of San 
Francisco Bay. Whe chief difference is in the greater remoteness of the Los Banos region 
from the seat of disturbance, if only one such seat be assumed. 


346 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


Another circumstance which weakens the suggestion of a local earthquake is the 
failure of the isoseismals below VII to carry out the suggestion by bulging into the Coast 
Ranges on the west or the flanks of the Sierra Nevada on the east. In the latitude of 
Los Banos, the high apparent intensity was confined to the valley-floor; altho farther 
south, near Cantua, this can not be affirmed. In view of the experiments of Professor 
Rogers, it seems probable that in the near future, by an active prosecution of such 
experiments coupled with close field observation, we shall arrive at an arithmetical 
expression for the coefficient which will enable us to reduce the apparent intensity of 
water-saturated alluvium to the true intensity due to vibration in homogeneous elastic 
rock. When that coefficient becomes available, it will perhaps be possible to determine 
whether or not the destructive effects exemplified in the San Joaquin Valley at Los 
Banos are referable to the conditions of the ground or to a local seismic disturbance. 
Until then the question must remain an open one. Analogy with other valley lands 
nearer the fault, where high apparent intensities are referable, both on the field evidence 
and in the light of Professor Rogers’ experiments, to local conditions, militates against 
the hypothesis of a quasi-independent earthquake. The remoteness of the region from 
the known fault and the high intensities on the flanks of the Coast Ranges indicated by 
the new landslides at Cantua, favor that hypothesis; but no positive conclusion can 
be reached at present. 


RELATION OF APPARENT INTENSITY TO KNOWN FAULTS. 


Altho the geology of California has been studied in detail at but few localities out- 
side of the gold belt of the Sierra Nevada, yet the general reconnaissance work that 
has been done by various geologists has brought to light many of the important faults 
in the state. Such as are known are indicated on map No. 1, without any attempt 
to discriminate between the varying degrees of certainty with which their existence has 
been determined. The map serves the double purpose of bringing together for the firs! 
time our knowledge of. the distribution of faults thruout the state, and of illuminat+ 
ing a brief discussion of the relation of apparent intensity to fault-lines. On 4 of these 
faults there have occurred 5 severely destructive earthquakes within the last 50 yeers. 
It thus behooves students of Californian seismology to become familiar with these st:uc- 
tural features of the state. A recent account of the Calabrian earthquake of September 
8, 1905, dealing particularly with the distribution of intensity,’ and the relation of that 
distribution to fault-lines known or inferred, gives an especial interest to the considera- 
tion of the faults of the Californian region at this time. In the preceding section of this 
report, it has been shown very definitely that abnormally high apparent intensities were 
developed on the valley-bottoms, and the cause of this has been referred in « general 
way to the incoherent and water-saturated condition of the materials underlying these 
valley-bottoms. In Calabria, in the account referred to, Professor Hobbs correlates 
the zones of exceptionally high intensity with lines of ancient faults, whih in some 
portions of the region are known on geological evidence to exist, and in others are sup- 
posed to exist because of the high intensities manifested. He does not recognize the 
character of the underlying formations as an important factor in producing different 
degrees of intensity, as inferred from destructive effects at the surface. in this respect 
his conclusions do not harmonize with those arrived at in the study of the California 
earthquake of April 18, 1906. It thus becomes a matter of interest to ascertain what, 
if any, influence was exercised by the known faults of California, other than that which 
was the seat of disturbance, upon the distribution of apparent intensiy, independently 





*W. H. Hobbs, The Geotectonic and Geodynamie Aspects of Calabria end. Northern Sicily. 
Leipzig, 1907. 


ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 347 


of that which was clearly due to the character of the geological formations. This ques- 
tion has been touched upon incidentally in the discussion of the relation of the valleys 
to distribution of apparent intensity, but it will be of advantage to review the facts 
here more systematically, tho quite briefly. 

In southern Oregon and in northeastern California, in Modoc, Shasta, Lassen, and 
Plumas Counties, the shock was so uniformly feeble that there is no suggestion of locally 
high intensity due to any cause. The same general statement is true of northeastern 
California, in Del Norte, Siskiyou, Humboldt, and Trinity Counties; but in this region 
some of the faults, particularly that of Redwood Mountain, were not farther from the 
seat of disturbance than certain localities farther south, where abnormally high apparent 
intensity was developed on valley-bottoms. If the Redwood Mountain fault had been 
a locus of movement, there can be little doubt, altho the settlements in that region are 
few and scattered, that we should have heard of the severity of the shock. No evidence, 
however, has come to hand indicative of any exceptional severity on or near the line 
of that fault. 

Along the eastern front of the Sierra Nevada, from Honey Lake and the T aylorsville 
district to Tejon Pass, altho there are many extensive faults, and altho on one of these 
there occurred a movement which caused the Inyo earthquake of 1872, yet there is no 
suggestion of any local movement on any of these on the morning of April 18, 1906. The 
intensity of the shock along this general fault-zone was about IV of the scale; but the 
movement was a slow, gentle swing characteristic of a heavy distant shock. 

Similarly, the numerous faults which traverse California south of Tehachapi may be 
left out of consideration, no shock at all having been felt over the greater part of the 
region, and but feebly in those parts where it was felt. 

There thus remain of the faults in California practically only those that fall within 
the zone of destruction, to merit serious consideration. The most northerly of these 
is the Mount St. Helena fault described by Osmont.!. This fault has a northwest-southeast 
strike, and a throw of not less than 2,000 feet. It forms a well-marked and little- 
degraded scarp on the southwest side of the mountain and the date of its principal 
movement is within the Quaternary period. The projection of this fault to the north- 
west is not known; to the southeast it undoubtedly passes beneath the floor of Napa 
Valley, in the vicinity of Calistoga. Neither on the slopes of the mountain nor at Calis- 
toga was there any evidence of abnormally high intensity, and the necessary inference 
is, therefore, that there was no movement on the fault at the time of the earthquake. 

The southwest front of the Berkeley Hills, and the extension of the same geomorphic 
feature farther south, forming the southwest front of the higher Mount Hamilton Range, 
is with little question a fault-scarp, or series of scarps, of Quaternary date, now more 
or less dissected and degraded. The northern extension of the fault-zone beyond San 
Pablo Bay is not known. It probably contributed to the definition of the western side 
of the ridge between Sonoma and Petaluma, but apparently did not traverse the middle 
part of Santa Rosa Valley, since the study of that region by Osmont failed to reveal it. 

This fault-zone is of peculiar interest from the point of view of the present discussion, 
since it appears to have been the seat of disturbance of the earthquake of 1868. At 
that time the fault-trace was marked by a crack at the surface, which was traceable 
for 20 miles or more along the base of the scarp slope, altho the amount of the move- 
ment was probably quite small. The trace of the fault is approximately parallel to the 
San Andreas Rift, and is 18 miles distant from it. As has already been suggested, this 
fault would seem a priori more susceptible to the influences which would make for re- 
newed movement than most other faults of the region. But there is no evidence that 
any movement occurred upon it. The intensity showed no abnormal increase along 





1 Loc. cit. 


348 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


the old fault-trace; and buildings at Berkeley, founded on rock, practically on the line 
of the fault, suffered little or no damage. 

The fault which is so well exposed in the sea-cliff south of Fort Point traverses the city 
of San Francisco in a southeasterly direction for an unknown distance. Along the line 
of its probable course, Mr. Wood has noted evidence of an increase of intensity. The 
fault in its projection seaward probably intersects the San Andreas fault beneath the 
Gulf of the Farallones. It is therefore possible that there was some slight distribution 
of the movement along this intersecting fault. 

The San Bruno fault-scarp, on the peninsula of San Francisco, south of the city, is 
well illustrated in Plate 15, and its structural relations are described in a paper by Andrew 
C. Lawson on the Geology of the San Francisco Peninsula.’ 

The base of the scarp is from 2.5 to 3 miles distant from the San Andreas Rift, and is 
nearly parallel to it. The fault is in two parts: a main fault with a throw of not less 
than 7,000 feet, which drops the Merced (Pliocene) strata against the older Franciscan 
rocks, and an auxiliary fault which drops a wedge of Franciscan strata between the 
main fault and the mass of San Bruno Mountain. The town of South San Francisco is 
on the lower slopes of a rocky spur of San Bruno Mountain, between the two faults, 7.e., 
it is on the dropt wedge of Franciscan rocks. In the water-saturated alluvium and sands 
of Merced Valley, the apparent intensity was high, ranging up to IX of the scale; but 
in South San Francisco, on rock foundation, it was notably lower, as appears from Mr. 
Crandall’s report. The situation of south San Francisco, between the two faults, is such 
that had a movement occurred on either, the damage to structures would have been 
accentuated. But the fact is that the damage was not so accentuated, and there is 
thus no warrant for supposing that any local fault movement occurred. 

One circumstance which, upon first thought, seems to contravene this conclusion, 
was the sudden outgush of water at one point at the base of the San Bruno scarp. This 
remarkable occurrence is described in another place, but may be mentioned here, for 
the purpose of bringing together the facts bearing on the question. The water issued, 
as near as can be determined, at a point on the slope immediately above the fault-trace 
of the auxiliary fault, in the underlying hard rocks, which are there mantled with an 
unknown thickness of sand, possibly 50 feet or more. The outgush of water is indica- 
tive of sudden compression of incoherent water-saturated sand, and does not necessarily 
imply a movement on the deeper fault. Along the line of the fault there are longi- 
tudinal depressions, and it is suggested that one of these was filled with sand, under 
conditions which did not permit of rapid drainage; so that the sand was saturated with 
water, which was expelled as the compressive wave traversed the locality. 

In the region to the southwest of the San Andreas Rift in San Mateo and Santa Cruz 
Counties there are several faults, most of which are represented on maps Nos. 21 and 22. 
No evidence of movement has been detected on any of them, altho the territory has 
been examined quite closely; nor does their presence appear in any way to have affected 
the disposition of the isoseismal curves. They nearly all traverse a country occupied by 
rocky mountainous slopes, and have considerable variation in orientation, altho the pre- 
vailing strike is northwesterly and southeasterly. One fault, however, viz., the San 
Gregorio fault, crosses 2 valleys — San Gregorio Valley and Pescadero Valley — in which 
the intensity of the shock was abnormally high. The independence of this high apparent 
intensity to the fault has been pointed out in another place. 

To the north of Black Mountain, on the northeast side of the San Andreas Rift, 
a branch fault leaves the Rift line a little south of Portola, at an angle of about 25°, 
and is traceable for about 8 miles on the lower northeastern flank of Black Mountain. 
Between this Black Mountain fault and San Andreas Rift there is enclosed a wedge of 


*U.S. Geological Survey, 15th Ann. Report. 





ISOSEISMALS: DISTRIBUTION OF APPARENT INTENSITY. 349 


ground in which the shock was of exceptional severity. It was traversed by numerous 
cracks, and there are other manifestations of acute disturbance of the ground, as set 
forth in the more detailed section of the report. In this case it is quite possible and 
even probable that the movement on the main fault in the line of the Rift was distributed 
to some slight extent along the branch fault. It is to be noted, in this connection, that to 
the south of Black Mountain there is a slight curvature in the course of the main fault 
to the eastward. This curvature would present an exceptional obstacle to the move- 
ment of the two crustal blocks, the one on the other, greatly increase friction, and so 
locally intensify the shock. It may thus be that the exceptional intensity in the Black 
Mountain mass, and the consequent bulging of the isoseismals on either side of the fault 
in this vicinity, is referable to this irregularity in the plane of the fault; and that the 
branch fault at Portola may be a means of relief from the excessive pressure locally in- 
duced by the irregularity. On the southwest side of the San Andreas Rift, and on the 
other side of the bulge in the fault-trace, is the Castle Rock fault, the strike of which 
branches from the main fault on the Rift at an angle of about 20°. Altho this fault has 
not been actually traced into the line of the Rift, there can be little doubt that it is a 
branch from that fault-zone and it probably bears the same structural relation to it that 
the Black Mountain fault does, 7.e., it serves as a means of relief for the exceptional 
local pressure due to the nearby irregularity in the main fault. There is, however, no 
observational evidence of any movement having occurred on the Castle Rock fault on 
April 18, altho it lies within the region of bulging isoseismals. 

In the Mount Hamilton Range, between Niles Canyon and Mount Hamilton, there 
are many faults; but none of them, so far as the information available will warrant a 
conclusion, appears to have affected in any way the distribution of intensity. Two of 
these, the Mission Peak fault, which is probably a branch from that on which cracks 
opened in 1868 near Haywards, and Mission Creek fault, pass close to the town of Niles. 
But the apparent intensity at Niles was less than on the flat alluvial tract to the west, 
and not greater than in the valley-land about Pleasanton and Livermore to the east ; and 
this circumstance amounts to a proof that no movement occurred on either of these 
faults. A similar conclusion may be drawn with reference to the Sunol fault, from the 
fact that the apparent intensity at Sunol was somewhat less than at Pleasanton, altho 
the former is nearer the Sunol fault than is the latter. In the country between the 
Haywards fault and the Sunol fault there are several minor faults, but there is no indica- 
tion in the distribution of intensity of movement having occurred on any of them. 
Similar statements are true of the fault zone extending from the vicinity of Benicia 
northward on the west side of the Sacramento Valley. 

In the canyon of Pajaro River, below Chittenden, there is an east-west fault whereby the 
Tertiary rocks on the north side have been dropt against the granitic rocks of the Gavilan 
Range on the south. This fault crosses the San Andreas Rift, and its known extent on 
either side of the Rift is within the zone of high intensity referable to the movement 
of April 18. There are here no especial features in the distribution of apparent inten- 
sity which suggest any movement on this fault. It is possible, however, that a slight 
movement took place on this fault, since the steel bridge over the Pajaro River, which 
is about on the intersection of the two faults, was distended 3.5 feet between its end piers, 
as shown in plate 65n, ina way that can not be altogether satisfactorily explained by the 
movement on the fault along the Rift. The direction of the chief displacement of the 
piers was about midway between the strikes of the two faults. 

In the Santa Lucia Range to the southwest of the Salinas Valley, there are several 
faults. The principal one runs along the northeast flank of the range on the edge of 
the Salinas Valley. The reasons for ascribing the high apparent intensity on the floor 
of the Salinas Valley to the character of the underlying formations, rather than to any 


3950 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


disturbance on this fault, have already been stated. Farther south, a fault runs parallel 
with the Salinas River in that portion of its course between Templeton and Dove; but 
here the apparent intensity was lower than in the valley lands both to the north and 
to the south. 

To the southwest of this is another parallel, but a longer fault, along the southwest 
side of the San Rafael Mountains. In the valley lands to the southwest of this, about 
San Luis Obispo, Edna, Arroyo Grande, and Santa Maria, the intensity rose from III 
to IV; but in view of the accumulation of evidence set forth in the preceding pages as 
to the influence exercised by alluviated bottoms upon the apparent intensity, this rise 
is more probably referred to the character of the ground than to proximity to this fault- 
line. South of Santa Maria is a region of frequent seismic disturbance, but no sharp 
shock of a local earthquake was felt there on April 18. 

It thus appears that in the territory extending from Humboldt County to Santa 
Barbara County, while there are about 40 faults known to geologists who have studied 
the region, there is no evidence of movement on any of them except in 3 cases. One of 
these is a branch from the fault-zone of the San Andreas Rift — the Black Mountain 
fault; another is a transverse fault intersecting the Rift in Pajaro Canyon; and the 
third is the fault which traverses the city of San Francisco and probably intersects the 
San Andreas fault beneath the Gulf of the Farallones. In these cases it is possible, in 
the light of the evidence, that some portion of the movement on the main fault was dis- 
tributed along intersecting faults. 


DIRECTIONS OF VIBRATORY MOVEMENT, 


GENERAL NOTE. 


The data for the discussion of the directions of propagation and vibration of the earth- 
waves is for the most part unsatisfactory and leads only to a conviction of the complex- 
ity of the general problem of earth movement. Apart from the intrinsic complexity of 
the subject, there were two conditions which were adverse to the securing of exact and 
significant information. The first of these was the lack of provision for obtaining instru- 
mental records of earthquake shocks thruout California. There were very few seismo- 
graphs installed in the state and such as were in existence proved in large measure inade- 
quate for the purpose for which they were intended. The second adverse condition was 
the hour at which the earthquake began. At its beginning most people were asleep, 
and the confusion incident to so rude an awakening was not conducive to sharp observa- 
tion. The chief trouble, however, inheres in the intricate and confused nature of the 
earth movement itself. A brief statement of the different kinds of movement involved 
in the commotion of the earth may be of service in the formulation of clear ideas of the 
nature of the shock in general and of the question of direction in particular. 

Usually the principal movement of the ground in an earthquake is vibratory. In the 
California earthquake there was, however, a mass movement in opposite directions on 
the two sides of the San Andreas fault. This mass movement was, as has been shown 
by the work of the Coast and Geodetic Survey, distributed over a wide zone on either 
side of the fault and diminished more or less regularly with distance from it. The move- 
ment was not vibratory except to a very limited extent; but it gave rise to the displace- 
ment of objects on the surface quite similar to that caused by the vibratory movement. 

Thus, in attempting to deduce the directions of propagation and vibration of the earth- 
waves from the phenomena of displaced objects or persons, it is necessary to discrimi- 
nate between the effects due to the mass movement and the true vibration of the ground. 
But this discrimination is only possible to a very limited extent, partly because the 
borders of the zone within which the mass movement caused the displacement of objects 
and persons are unknown, and partly because the two kinds of movement overlapt, con- 
spiring to produce a single effect. 

When we come to consider the earth-waves generated by the movement on the fault, 
probably as an effect of friction, it must be at once apparent that these waves emanated 
from innumerable points on a plane, one dimension of which is about 270 miles and the 
other probably 20 miles or more. On this plane, if we judge from the course of the 
fault-trace, there were at certain places inequalities which offered exceptional resistance 
to movement, and at these the jar was exceptionally heavy and dominated the vibrations 
emanating from portions of freer movement. From all parts of the fault-plane, there- 
fore, waves of various amplitudes were propagated in all directions, and their paths 
intersected. The consequent interference would in part make for neutralization and 
in part for intensification of the vibratory movement. It is thus evident that the effects 
produced by the emergence of these waves at the surface, or by the propagation of those 
emanating from the more superficial portions of the fault along the surface, could be 
systematically disposed only if the following conditions obtained: 

351 


302 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


1. That the fault-plane were uniformly even or systematically uneven. 

2. That the rock affected both by the rupture and by the vibrations were homo- 

geneous thruout. 

3. And that the stress which gave rise to the rupture were uniform for the entire 

extent of the fault. 

It is fairly certain that none of these conditions actually did obtain; and we might, 
therefore, predict that the disposition of the effects of the shock, and particularly of 
the heavier portions of the shock, from which directions might be inferred, would be 
irregular, tho distribution of the intensity in the aggregate might be fairly symmetrical. 

This conclusion has been reached on the tacit assumption that there is but one kind of 
earth-wave or vibratory movement. But it is highly probable on theoretical grounds, 
and the theory is supported by experiment, that the vibration of the earth generated 
at the fault resolves itself into two quite distinct waves having quite different rates of 
propagation and direction of vibration. One of these is the longitudinal wave, so called 
because the vibrations are parallel to the direction of propagation, and the other is the 
transverse wave in which the vibrations are normal to the direction of propagation. 
The rate of propagation of the longitudinal waves in highly elastic rocks is nearly double 
that of the transverse waves. It will thus be evident that at any locality within the 
zone of disturbance an object may be shaken or displaced by the emergence of the longi- 
tudinal wave at that point, and that the movement due to the emergence of the transverse 
wave may be superimposed upon this either before or after it has come to rest. The 
resultant effect will be accordingly difficult to interpret as to the direction of the vibra- 
tion for either wave. When, however, the locality in question is sufficiently far removed 
from the fault, the interval between the emergence of the two waves may be sufficiently 
long to permit of the effect of the first being noted before that of the second is super- 
imposed. 

In the case of the California earthquake, the movement of the ground was compli- 
cated by the fact that both longitudinal and transverse waves were propagated in direc- 
tions nearly parallel to the surface from the superficial portion of the fault, and these 
for many miles out from the fault might be expected to give rise to movements discord- 
ant with those due to the arrival of similar waves from the deeper portions of the fault. 
It would thus seem, from the considerations thus far presented, that regularity in the 
disposition of the effects of the shock upon which a judgment as to the direction of the 
vibration nfight be based, was about the last thing to be expected. In other words, it 
would seem, on a priori grounds, to be a hopeless task to plot upon a map of California 
the direction of propagation and vibration of the earth-waves. The hopelessness of 
the task is intensified when certain other considerations are taken into account. For 
example, there were secondary short surface-waves of low speed and high amplitude 
observed in many parts of California, which are quite different from the high-velocity 
waves thus far discust. These undoubtedly had an important effect in the displacement 
of objects and persons, and so influenced judgments as to the direction of movement. 
Similarly on the alluvial bottoms of the rivers the ground lurched consistently toward 
the stream trench, whatever the orientation of the latter might be; and the phenomena 
arising from such movement gave rise to judgments as to the direction of the earth-waves 
which were of course erroneous. 

Added to all this was the general fact that those who contributed reports from various 
parts of the state to the general account of the earthquake in many cases based their 
judgment as to the direction of the shock upon the displacement of portions of structures, 
such as chimneys, or of objects within buildings. This kind of evidence was in most 
cases untrustworthy, and could lead to reliable conclusions only when treated critically 
and statistically so as to obtain a general result. Even the displacement of buildings 


DIRECTIONS OF VIBRATORY MOVEMENT. 353 


themselves was no criterion of the direction of vibration of the ground except when 
these rested upon uniform foundations. Buildings upon poorly braced underpinning, 
such as are common in California, collapsed in consequence of the swaying; but the 
direction of the horizontal element in the collapse was more often determined by the 
nature of the structure than by the dominant movement of the ground. Even in ceme- 
teries the direction of overthrow of simple shafts, circular or Square in cross-section, 
failed to indicate the direction of the dominant movement, since within a small radius 
they fell to all points of the compass. The indication of the cemeteries was that the 
movement of the ground was very complex; the shafts were started swaying upon their 
pedestals, and the direction of their fall was for the most part accidental, as the rocking 
increased in violence due to the accumulating impulse. Treated statistically, however, 
the larger cemeteries afforded some indication as to the direction of the dominant move- 
ment of the ground. 

In view of what has been said, it will not be surprising that the effort to interpret the 
reports from various parts of the state regarding the direction of movement of the ground 
has been unsuccessful. The reports were in general contradictory for the same locality 
whenever there were two or more independent observers. It was evident that most 
of the reports were based on evidence of the movement of the ground which had no sig- 
nificance in isolated instances, and a general critical review of the evidence was attempted 
only by a few observers. It was also evident that in many cases the effects of one move- 
ment had imprest one observer, while the effects of a different movement had attracted 
the attention of another. In these cases the contradiction was more apparent than 
real, but there was generally doubt as to the correctness of both. Even when the reports 
were perfectly satisfactory records of facts, the latter in many cases permitted of no safe 
inference as to direction of movement except that there were several movements in 
several directions, and that the sequence of these could not be determined. 

The following report from E. G. Still of Livermore is a good example of an excellent 
account of the important facts bearing on the question of directions: 


The Railway Company’s big 20,000-gallon water-tank fell to the north-northeast. Tomb- 
stones in one graveyard fell in many directions. Lamps swung in an oval, extending about 
east and west. ‘The motion seemed to shake my bed north and south at first, then in a 
circular motion, then sideways and in every direction. Water spilt from full tanks, mostly 
on east and west sides. 


There is a suggestion here of two dominant movements — a northerly and southerly, 
and an easterly and westerly, the former being the earlier. But Mr. Crandall, for the 
same territory, reports that the general direction of motion, based on the observed spill- 
ing of liquids and swaying of suspended objects, was northwest and southeast. In 
most cases the reports consist of a statement of opinion as to the direction of movement, 
without the facts upon which the opinion is based. 


oo4 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


EFFECTS OF THE EARTHQUAKE ON HOUSES IN SAN MATEO AND BURLINGAME. 
By Rosert ANDERSON. 


Immediately following the earthquake of April 18, 1906, a detailed study was made 
by the writer’ of over 1,000 houses in San Mateo County. This work was carried on 
under the direction of Dr. J. C. Branner, of Stanford University. The houses examined 
included all those in the town of San Mateo and on the hills west of it in Burlingame and 
San Mateo Heights, as well as many in Homestead, Belmont, San Carlos, and Redwood 
City. Examination was made of all details that could possibly give a clue to the char- 
acter of the earthquake shock, and its effects upon movable things. 

San Mateo is a mile west of San Francisco Bay, and about 3 miles northeast of the 
San Andreas fault along which the earthquake had its origin. All the houses included 
in this investigation lie between 1 mile and 4 miles in a northeast direction away from 
the nearest points along the fault. A range of hills from 500 to 700 feet high lies between 
the fault and the valley bordering the bay where San Mateo and Redwood City are situ- 
ated. The houses examined at Burlingame and San Mateo Heights stand on the north- 
east flank Of this range of foot-hills. It was hoped that the directions of the streets 
of San Mateo, parallel and at right angles to the fault, would throw some light upon the 
relations of location to the center of disturbance. 


CRITERIA. 
The following classes of evidence were examined, with especial regard to the direc- 
tion and relative force of the shock: 

1. The wreckage of brick, stone, and wooden buildings, the parting of walls, and 
displacement of parts. 

2. The cracking of foundations and the movement of houses on them. 

3. The cracking, crumbling, shifting, falling, jumping, and twisting of brick chimneys 
above and below roofs, as well as of cement, terra-cotta, and other chimneys. 

4. The cracking and falling of plaster and coatings of cement on the interior and 

exterior of buildings. 
The sliding, falling, and jumping of dishes, lamps, bric-i-brac, pictures, books, 
potted plants, and all such loose articles. 

6. The sliding, tipping, jumping, and turning of furniture, such as bureaus, tables, 

“ bookeases, beds, pianos, stoves, safes, machinery, and all other large mov- 
able articles. 

7. The falling, sliding, twisting, and jumping of tanks, towers, porches, pillars, 
underpinnings, gate-posts, mantelpieces, derricks, ete. 

8. The breaking and offsetting of pipes, bending of bolts, shifting of stove-pipes, 
bulging of windows with lead seams, and the raising and lowering of sliding 
windows. 

9. The shifting of loose piles of lumber, stove, and cord wood, and various materials, 
and the sliding of articles on rough and smooth surfaces. 

10. The swinging of hanging articles, pictures, lamps, pendulums, ete. 

11. The breaking of wire connections, such as telephone, telegraph, and light wires. 

12. The remaining in position of articles at liberty to fall in certain limited directions. 

13. The parting of ground at base of telegraph poles and cracking of ground elsewhere. 

14. The spilling and splashing of liquids. 

15. The feelings, experiences, and testimony of people. 

This paper gives only the general results of all the data, the more important facts 
alone being tabulated. | 


Or 





1 Valuable aid was received from P. C. Edwards, A. L. Motz, and A. F. Taggart, students of Stanford 
University. 


DIRECTIONS OF VIBRATORY MOVEMENT. 355 


DAMAGES. 


The effects upon brick and stone buildings. —The region covered has only about 
25 buildings of brick and stone. In most cases, the damage done to these structures 
was far more severe than to those of wood. Usually a considerable part of some of the 
walls crumbled away, while the rest were left standing with large and small cracks in 
them. The tops of walls below the roofs usually suffered most, while lines of weakness 
in walls, caused by the presence of windows, arches, and other apertures, gave way to 
cracking more readily than other parts. A few brick buildings were totally demolished, 
as in the case of the long, brick, railroad warehouse at San Mateo. (See plate 98a.) 
The whole center of the picture to the right and left of the tower was occupied by the 
building, of which only the foundation remains. 

Some brick buildings, stoutly constructed or wedged in on business blocks among 
structures that acted as common supports, withstood the earthquake well, altho some 
portion was almost invariably damaged. The triangular gable ends of brick buildings 
rarely remained in place. The cracking in brick structures seldom past thru the brick 
themselves, but usually took place along lines of cementing. The very few stone build- 
ings in the vicinity of San Mateo were almost shaken to pieces. 

Wooden buildings. — In general, wooden structures suffered much less severely than 
those of brick or stone, tho the shock was felt just as heavily in them and the damage 
to loose articles was just as great. The buildings least damaged were small wooden 
houses, which were practically proof against the earthquake. 

Foundations. — The effect of the earthquake on foundations was of great importance, 
for the foundations were responsible for much of the damage to upper parts of buildings. 
With reference to this point, the buildings have been divided into 3 groups — those 
having foundations of wood, of concrete, or of brick. Wooden foundations are of various 
kinds, and the group includes all houses resting directly on the ground, or on wooden 
sills or wooden underpinning, even if the latter are supported on brick piers; it also 
includes all other buildings not having foundations of hard materials, such as concrete, 
brick, or stone. 

The foundations were examined for evidences of movements in various directions, 
and for the purpose of learning the relative amounts of cracking to which each was sub- 
jected. The accompanying table gives the results: 


Number of houses examined, with number of houses moved, and number of foundations cracked. 


























BELMONT, BURLINGAME 
San Mareo., ReEDwoop. HOMESTEAD, AND SAN Tora. 
AND SANCARLOS.| Marro Hits. 
aac te Te i beceehe|-s =i] 2. lee 
n® ag So |no|oa3/8d | mb! os |/.9d| 2B] a 5]/sd]| 2d ou - z| oo | oS 
Character of. ae Ae aa 2 ey 23 ea Se lee 25 a ate z o 5 z ae ase 
foundation | §8 | 50 | Ug | 38] 28 32/158) 65 193/68) 50/382 55 09 |&°a| 33 i|sus 
me | mA | BS me ime | B65 mg ma] BS ms lea) Se) me | me | oe] BE | ess 
: Fe : cs cs os Po} ge [ALS 
Wood . 266 eee Oo woo ~of 00 2 “sh 38. 1 387 fT fad OF fale oe se 
Concrete . 176 51 43 7 TONE eee LAs 1 | 41 1 7 \*225 59 | 26 51 ao 
Brick . 160 51 63 8 S 1 160 Ks 4. 46_ 4 26— 230 58 26_ 94 41 
Total 602 | 149 | 106 | 78 | 33 TGs 2 5 | 95 6 | 33 | 842 | 190 | 23 | 145 
tt 









































The total number of houses falling into these groups is 842. Of these 23 per cent 
moved on their foundations. In most cases the movement was not so great as to neces- 
sitate the returning of the house to its original position, but this had often to be done, 
since many houses were rendered unstable. The distance moved varied from less than 
0.25 inch to several inches, and in cases of special severity houses were thrown a foot or 
more off their underpinnings or foundations. Those on wooden foundations moved 
the least — 17 per cent in a total of 387 such houses. There were 225 houses on concrete 


306 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


foundations and 230 on foundations of brick, and in each case 26 per cent moved. Out 
of the total of 455 concrete and brick foundations, 32 per cent were cracked, as follows: 
23 per cent of the concrete foundations were cracked, while 41 per cent of the brick 
foundations were cracked. Nor does this proportion fully represent the facts, for it 
was only in rare cases that the cracking of the concrete was of much importance; while, 
on the other hand, the damage to the brick foundations was often sufficient to endanger 
the stability of the house. The wooden foundations were rarely damaged. In cases where 
houses had especially heavy foundations, the damage was noticeably slighter. Heavy 
concrete foundations rendered structures almost immune to the shock. Not many 
heavy concrete bridges, for instance, were harmed. In a store that rests on the massive 
concrete foundation of a bridge crossing the creek in San Mateo, absolutely nothing 
was disturbed, altho the building overhung the creek about 7 feet. None of the many 
loose articles on the shelves fell, and a high top-heavy machine stood perfectly. 

The falling of brick chimneys suggests the possible influence of the foundations upon 
these structures. Of all the chimneys on houses having wood foundations, 91 per cent 
fell; of those on houses with concrete foundations, 81 per cent fell; of those on houses 
with brick foundations, 88 per cent fell. A truer relation is given by taking merely 
those on the flat land at San Mateo and Redwood City, where the cases are strictly com- 
parable. Of these the proportions in the same order are 93 per cent, 98 per cent, and 
96 per cent. The disadvantage of brick foundations is further attested by the greater 
damage to plaster in houses built on them. 

Brick chimneys. — In the region studied, the tops of 88 per cent of all the brick chim- 
neys fell at the time of the earthquake. This proportion is for the whole region. The 
varying proportions in the different localities are shown in the following table: 


Table showing the number of brick chimneys examined, with per cent which fell, from houses on 
various foundations. 























BELMONT, BURLINGAME 
San MATEO. Repwoop Ciry. | Homestrap, AND | AND SAN MATrKo Toran, 
CARLOs. His, 
Charact f n mn Spe n n on n - n Dey n 3 
foundaiiona: pad Ms 2D > 2 oe 2 Be Ps Be 3 m! 2 
a4 a. a-d a a.8 as ag aS a8 ae Bas 
He | fe’) ge | 2 | ga | Be | Be | BS | Be | gs | Se 
es | 6 | ee |e fee ye [esa | ai 
Wood. « 280 257 64 63 OW 44 15 11 410 375 91 
Concrete . 187 165 9 8 3 3 85 oo 284 231 81 
Brick sae 256 242 10 9 20 24 110 88 403 363 28 
Totaly (eB 664 83 80 81 val 210 154 1097 969 88 





























Besides the falling of the tops, a large proportion of the chimneys that suffered this 
loss, as well as a great many that did not, were injured or cracked at the base or some- 
where within the house. Hconomically, the damage below the roof is the most serious, 
as it is difficult to remedy and is a menace to the safety of the building. Some chimneys 
crumbled away entirely. This happened most frequently to those built on the outside 
of the house, in which case they usually fell away from the house, doing little harm. 
This may be considered a point in favor of exterior flues, inasmuch as the wreckage to 
houses due to the chimneys falling through the roofs, as well as the difficulty of repairing 
interior flues, is avoided. On the other hand, the unsupported exterior chimneys show 
a greater tendency to fall. Ash-boxes at the bases. of chimneys weakened them at 
these parts, and made them more liable to injury. Only 12 per cent of the tops of the 
brick chimneys remained standing, the reasons for their standing being generally found 
in the construction of the chimneys themselves. The use of cement and lime instead 
of simply lime mortar, accounts for the standing of many, although the use of cement 


DIRECTIONS OF VIBRATORY MOVEMENT. 307 


did not always insure their safety. Many that stood were found not to be built up from 
the ground, but to rest on shelves somewhere within the house. This method of build- 
ing seemed to preserve the chimney intact in the majority of cases. A few chimneys 
owe their preservation to their low, solid structure above the roof ; many did not fall 
because they were well-braced, either by being inclosed in a wooden casing or a coating 
of cement, or by being held by iron rods clamped into the brick. A striking example 
of the advantage of an iron rod as support was that of a 2-story house in San Mateo. 
This house had a brick foundation and a slender chimney 14 fect high, supported by an 
iron rod. The chimney stood perfectly. 

A great many chimneys that stood well above the roof were badly damaged at the 
base or within the house, and many were cracked above the roof and shifted a short 
distance horizontally. The use of cement in the mortar saved the chimneys in some 
instances, but a common effect of the shock on chimneys so built was to crack them 
somewhere and make them fall in one piece. In this way solid masses of great weight 
were sometimes pitched on to roofs and other parts of buildings, and the result was 
much greater damage to the house than was caused by chimneys built with lime mortar. 
Chimneys laid with lime mortar generally broke in many pieces or fell as loose bricks. 
The use of cement below the roof was apparently helpful, as the chief danger to that 
part of the chimney is from cracking rather than from falling, and the cement is much 
less apt to crack than the lime. The use of lime mortar above the roof is better, unless 
the chimney is to be boxed and braced. The construction of boxes around chimney 
tops, and the bracing with iron rods, are two simple and efficient preventives to the 
falling of chimneys of which comparatively few have made use. 

Chimneys other than brick. — Many of the small houses of San Mateo County use terra- 
cotta thimbles or chimney pots, in place of brick chimneys. Their efficiency against 
earthquakes is conclusively shown by the fact that a large proportion of them stood 
unhurt, even when built in several sections. From 90 to 95 per cent of these chimneys 
past through the earthquake without harm. Galvanized-iron pipes, and stove pipes 
used as chimneys, were likewise unhurt in most cases. The few chimneys that were 
built entirely of concrete proved to be much stronger than those of brick. 

Plaster. — In almost all houses with plastered walls, the plaster was cracked more or 
less seriously or broken off in sheets. The plaster or stucco on the outside of houses 
was badly damaged. In the majority of the houses, some of the walls — usually not all — 
were seamed with small cracks which ran in every direction and frequently in lines 
parallel with the laths. In other cases the cracks were wide and the walls were in large 
part laid bare. 

The second table on page 365 gives the statistics regarding the cracking of the plaster. 
The first column includes the cases in which the plaster was almost unhurt or only 
slightly cracked. Most of these buildings did not require replastering. The second 
and third groups include the buildings more seriously damaged. Replastering was 
necessary in the second and third groups. The plaster on the ceilings of houses was 
much less affected than that on the side walls, and in the majority of cases was unhurt. 
In 2-story houses the plaster was rarely damaged as severely on the second floor as 
on the first floor, and in wooden houses of three stories it was often observed that the 
plaster on the third floor was uninjured. This restriction of the damage to the ground 
floor may be due to the breaking of the plaster by short, sharp movements near the 
ground, which were translated above into the swaying of the entire upper story. That 
the plaster did not crack much on ceilings was probably due to the fact that the ceilings 
(and the floors above) were not subjected to so much strain because they moved as one 
piece. Thick coatings and varieties of hard plaster seem to have been less damaged. 
New plaster not yet dry was not affected in the few cases observed. 


308 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


Dishes, etc. —'There were few houses in which something did not move or fall a notice- 
able distance, and yet few in which everything moved or fell. There was little regularity, 
even in the same house, in the amount of movement of loose objects. Innumerable 
instances of seemingly capricious variation could be cited. The earthquake resulted 
in severe damage to breakables and heavy loss of dishes and bric-A-brac. Approximate 
figures as to the amount of such damage are given in the table on page 365. In houses 
where only a few dishes fell the damage was considered slight. Those losing about 
half of the breakables are shown in the second column, and all of the more severe cases 
are placed in column 3. The percentages are at best only approximate. In the valley 
about 40 per cent of the houses lost slightly, and 40 per cent lost heavily, the loss in 
the remaining 20 per cent being intermediate. On the hills 74 per cent of the houses 
lost but little, and even in other cases the loss was not great. Many dishes were saved 
by raised borders on shelves on which they were standing. It often happened that loose 
articles fell from the lower shelves in pantries, etc., and remained on the topmost ones. 

Windows. — It is an interesting fact that out of a total of thousands of windows in 
the area covered by this investigation, only a few were broken. Leaving out of account 
the windows of houses that were thrown down, the total number broken by the shaking 
or compression of the walls, or in other ways directly due to the shock, was probably 
not greater than 40. In several nurseries only a few panes were broken in many glass- 
covered hot-houses. The same general fact holds true over the whole of the San Fran- 
cisco Peninsula, and in other regions affected by the earthquake that were visited by 
the writer. The majority of the windows that were broken were in brick buildings. 
That the windows were subjected to great stresses is shown by the fact that many of 
those made of parts joined by lead bulged considerably, and many were thrown upward 
with sufficient force to break their locks. In about 20 per cent of the cases where win- 
dows were raised in this way the glass was broken. 

A resistant type of structure. — The data collected in this region appear to show that 
a house, to withstand an earthquake, should be constructed about as follows: The build- 
ing should be of wood, and a wooden sill should be bolted to a deep-laid concrete founda- 
tion, the top of which should be but little above the level of the ground. It should be 
ceiled with wood within. Shelves for dishes should be closed in with doors, or should 
at least have strips along the front edges. The chimneys should be laid with cement 
mortar and boxed from a foot or two below the roof to the top, and the parts above 
the roof should be braced with iron rods. The lower the structure the less strain it will 
be subjected to. Such a building would be practically proof against earthquakes having 
an intensity below X of the Rossi-Forel scale. 


THE MANNER AND DIRECTION OF MOVEMENT. 


Kinds of movements. — 'The shock of the earthquake was heavy enough to cause almost 
everything to move somewhat, and heavy objects were displaced as often as lighter ones, 
There were many cases of inconsistency in the movements, such as the displacement 
of heavy articles like pianos and stoves, where frail cups or vases remained in place; 
or such as the difference in motion exhibited by articles standing side by side. In 
many cases chimneys were thrown a distance of 6, 10, 15, and even 20 feet; a vase was 
thrown 6 feet, an accordion 4 feet, milk 8 feet. Hanging things were set in motion, 
liquids were spilt, and loose articles tipt over. 

Upward movements in many different places were attested by the fact that sliding 
windows were raised several inches with such foree as to break the iron latches that 
held them down. Possibly these windows were jerked up by their weights, which 
would have been thrown down with force had the houses been subjected to sharp verti- 





* Steel frames and reénforced concrete structures are also of course eminently well adapted to resist 
earthquake shocks of high intensity, A.C. L. 


DIRECTIONS OF VIBRATORY MOVEMENT. 309 


cal movements. In Prince Poniatowski’s house, which stands on the hills at an altitude 
of about 500 feet, a mile from the fault-line, all the windows — over 30 in number— 
were so raised. It is believed that all of the windows in this case were of the kind that 
are balanced by weights hanging within the frame. In many places on low land the same 
thing occurred. In one case a baby’s cot Jumped up and down, breaking its castors. 

Bodies frequently assumed positions such as would have been imparted by twisting 
movements. This was true in the case of many houses, turrets, articles of furniture, 
hanging pictures, and chimneys. The apparent twists were both in the positive and the 
negative direction, and varied from a few degrees to 180 degrees. In the opinion of 
the writer, such positions were the result of a complication of movements rather than of 
a twisting motion. The twisted position of furniture was often ascribable to the rolling 
of the castors. Dishes, vases, etc., could easily change their orientation, especially 
if they were tipt up, as was frequently done. But the majority of articles were caused 
to shift their position horizontally, in one or more direct lines. A large number of houses 
slid on their foundations, dishes and books slid off their shelves, and but few things 
failed to change position. 

Movement of houses. — One of the principal objects of this investigation was to find 
out in what direction houses moved on their foundations. Data were gathered concern- 
ing 842 wood, concrete, and brick foundations in regard to which it could be learned 
whether or not movement of the superstructure had taken place. Of this number 190, 
or 23 per cent, gave clear evidence of movement. In each case the direction and dis- 
tance were tabulated. The directions are given in the following table. The distances 
are given in the first table on page 365. 


Table showing direction of movements of houses on their foundations (total number of observations, 190). 






























































Group 1. Group 2. Group 1. Movements in directions 
Movements Movements Movements of Groups 1 and 2 
NW. and SW. NE. and SE. N.and S. combined. 
Localities, ; 
SW. NE. NW.| W. | SW. | SW. | NW. 
NW.| W. |SW.| and|NE.| E. | SE, | and Ss. N. and | and | and | and | and 
NW. SE. NE. E. SE. | NE. | SE. 
San Mateo . 25 ae235 4) 40 4 18 Sls aero Z 4 4 = ae 2 3 5 5 
Redwood ter rch, © 8 Tie Lee LO De leat 1 2 ene eerie litre et 
Belmont, Homestead 
AMG mans OATlOS. als alee cate ol ty ee sa SE ee eS i eer, el (ee el eee | eee ee 
Burlingame and San 
Na Teorellsas ee eoremeaeye al) 2 dy wlteee era renee is Meta Roce Meas (Pe eeears 2 ao 
Hbotainia ck) seems} of |rod 44, 1D OP LOLS he 5 6 2 2 3 5 * ‘ 
Group totals ... 125 36 8 17 
— — | 
Group per cents . . 65 19 6 9 




















Moved either SW. or NE., or in both directions, 31 per cent of total; moved either NW. or SE., or in 
both directions, 27 per cent of total. 

The majority of houses that shifted moved southwest and northwest, or combinations 
of these directions. The west movements tabulated in practically every case were a 
combination of movement of the house over the edge of the foundation to the northwest 
and southwest equal distances, so that the effect was the same as from a single move- 
ment west. It was not known whether there had been a single shift west, or two at 
right angles southwest and northwest. The author inclines to the belief that there 
were two main movements causing houses to shift southwest and northwest, rather than 
one in an east and west line, inasmuch as so many of the movements were simply south- 
west or northwest, or not directly west. The movements tabulated in the southwest 
and northwest column are those cases in which both movements affected the house, one 


360 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


predominating over the other. Grouping together all movements recorded as north- 
west and southwest and west, it is shown that 65.5 per cent of all the houses moving 
shifted in these directions. The second group of the table includes all movement in 
directions opposite to those of group 1 — that is northeast, east, and southeast. These 
make up 19 per cent more of the total. In the third group are included all those moving 
back and forth in the directions of groups 1 and 2, or partly in one main direction and 
partly opposite to the other main direction. These comprize 9 per cent. If, then, as 
the writer supposes, the west and east directions may be eliminated by being separated 
into their components, there will be 93.5 per cent of the total number that moved north- 
west, southwest, northeast, and southeast. 

Movement of chimneys. — The great majority of chimneys in the region under discus- 
sion are of brick. They are of many different shapes and sizes, in different positions 
on the roofs, of various materials, and are affected by structural variations and by age. 
They could not be expected to show perfect consistency in the direction of fall, but 
statistics were gathered in order to find out the tendency of the majority and their value 
as indicators of direction and intensity. 

In the following table the brick chimneys are grouped according to whether they 
fell in the direction of the slope of the roof on which they stood, obliquely, or at right 
angles to this; directly opposite to this, up the roof ; or according to whether they 
jumped. Those not falling form another group, of which a few shifted horizontally. 
The majority of streets on which the houses enumerated in this paper are situated, run 
in northwest and southeast, and southwest and northeast directions, so that the slopes 
of roofs are generally in those directions. More slope northwest and southeast than 
southwest and northeast. These directions of roof-slope make themselves apparent in 
the table, inasmuch as the slope of the roof exerts a marked control over the direction in 
which a chimney falls. 


Table showing the directions in which brick chimneys moved. 
























































Chimneys which fell down the || Chimneys which fell in a direction oblique or opposite to the Total movement in all 
roof, t.e. with the roof-slope. roof-slope, and those shifting or jumping. directions. 
Number | Number P 
Direc- ree Per cent by ates falling | Number | Number Total Per cent by be ae Rtg 
tion, directions. |jobliquely| opposite | jumped, | shifted. . | directions. . ° 
fell. io Tork aae moved, directions, 
NW. 175 31 ( 8 4 10 5 27 LON 202 24 | 
SW. 121) og we ei 7 8 1 31 | 12 6 22 152 1g (52 
NE. 102 18 ( 42 19 3 AO i eee ee 26 LO a 19 128 15 { 24 
SE. 133 24 ‘are 14 a 2 2 25 9 | 158 19 | 
NNW. 1 0.25 Lb. Gh ecoeee La eee 16 6 i Wy 2 
WNW. 1 0.25 LD. Pik Sc tevecell ete ie eae 15 6 | 19 16 2 7 
WS Wee aac. eae oo | ee ata 1 | ee 6 2) 6 7 1 
SSW. 1 0.25\ , 13: ( Vigese scien lah Pa ei a ai 13 5°} 14 2 
SSE, SE eee | ares ao AIF i Meeps rer Rat heh ee | aire Dar 8 12 rte 15.5 12 1 
BSE de Ai hceare sd beens LO sell niceties, a delay Sete le 10 3 sos 10 Il. 
EN EY: il) See ee 8 De WN ete eeetse, pees okie 9 3 9 1 
NNE 1 0.25 12 1+ Pel es See ae ee 12 5 | 14 2 
Ww. 5 teers 21 1 ined SAG 23 ae ae 28 31 
b. 7 ea PD IR i ME Sire 1 i 12 4 | 19 2; 5 
N. é 1 8! gules uae tL eee ae ae 9 Sea 14 2 
S. 8 t dPeeant ao. Bieee fens Pie Meas 22 8.54 115 30 i\ 6 
Total 1560 2205 325. 431 59 270 
Southwest-northeast, 40 p. ct. Northwest-southeast, 19 p. et. Northwest-southeast, 43 p. ct. 
Northwest-southeast, 55 p. ct. Southwest-northeast, 22 p. et. Southwest-northeast 33 p. ct. 
: 60 per cent of all that fell. Fell in known directions . . . ee re eee oe eT 
2 22 per cent of all that fell. Caved away and fell in doubtful directions | ae eeOn 
3 3 per cent of all that fell, aa 
43 per cent of all that fell, Total fell wo cee ote Liste Tae a teehee) een Oe 922 
5 7 per cent of all that did not fall. Shifted’ «tae. lu ee ee oe eye cee Pee 9 
Stood without falling . . . . . . eee, 118 
Total number of chimneys . . .... , 3 1049 








DIRECTIONS OF VIBRATORY MOVEMENT. 361 


It will be seen from the preceding table that out of a total of 922 brick-chimneys that 
fell, 60 per cent went down the roof, while only 3 per cent fell in the opposite direction : 
22 per cent fell obliquely, and 3 per cent with a leap apparently regardless of the roof. 
The predominance of the northwest and southwest directions, however, does not seem 
to be wholly due to the roof-slope. The table shows that in each division the north- 
west-southeast and northeast-southwest directions of movement are in the majority, 
even tho the chimneys have fallen in a direction contrary to the slope of the roof. 
The evidence here is not of the best, but there certainly seems to be a tendency toward 
motion in the same directions as those dominant in the case of the houses themselves. 
It may be supposed that chimneys fell in those directions owing to the movement of the 
house, but the majority of chimneys falling came from houses that were not dislocated. 

The evidence of the chimneys falling obliquely, up the roof, shifting, and jumping 
was the best, since they moved without regard or in opposition to structural influence. 
Among these much the largest number of movements in any two directions were north- 
west and southwest, and the next largest number just opposite. The northwest-south- 
east and southwest-northeast movements, then, were in the majority, making a total 
of 41 per cent, while a majority of those remaining moved in directions intermediate. 

Movement of dishes, books, etc. —Such loose articles as books, dishes, bric-d-brac, 
and lamps are, as a rule, free to fall or slide as they will, but in this region, especially 
in the town of San Mateo, the shelves on which many of them stood faced northwest, 
southwest, northeast, and southeast. The possible directions for falling in such cases 
were limited and this detracts somewhat from the value of the figures in the table. 


Table showing percentage of directions in which dishes moved. 





Direction. | Per cent moved, by directions. || Direction. | Per cent moved, by directions. 














Nw. 22 W. 4 

SW. 27 49 3 ., 3} 7 
NE. 20 A N. 1.5) ; 
SE. 20 S. 25 5 














SW. to NE., 47 per cent; NW. to SE., 42 per cent. 


Of objects overthrown, 89 per cent fell in one of these four directions. Tho many of 
the movements were determined solely by the direction in which the shelves faced, still 
the small number of movements in intermediate directions favors the idea that north- 
west and southwest and opposite movements predominate, for many of the cases recorded 
were of articles free to fall in any way whatsoever, and others were of articles that slid 
some distance along shelves without falling off. The east and west movements were 
more important than those north and south, showing a tendency in that way. 

As to the cases in which dishes remained in position without appreciable shift on 
shelves facing in the four main directions of movement, the southwest-facing shelves 
were most of them left empty, and there was a much greater number of cases in which 
dishes remained stationary when it seemed natural for them to fall northwest, northeast, 
or southeast. 

The case of a town library is especially worthy of mention: of books facing southeast, 
none fell; of those facing northwest, a few fell; of those facing southwest, all fell. 

Movement of furniture, etc. —These data include facts concerning the direction of 
movement of pianos, stoves, tables, bookcases, beds, bureaus, counters, cases, mantel- 
pieces, safes, deposits of merchandise, and the like. These were generally free to move 
in all or most directions. The way in which the furniture was moved was learned at 
every house, and the results tabulated by regarding every direction of movement in 
any one house as a unit. Hach unit, or case of movement, therefore, usually represents 
several individual movements. 


REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


Table giving data in regard to the moving of furniture. 











Te 
1 dep Rereontfge © 135 wateh srtiolcadl in sy ana liey RERSeMPES = c2 arta epeesiad 
Directions. furniture, ete,, specie) ere Directions, furniture, ete., pk ee 

moved, moved, — moved. : “moved, a 

NW. 19 14 SSE. 2 

SW. 31 6 ESE. 0.3 

NE. 18 4 ENE. 0.3 

SE. 11 6 NNE 0.3 a 
NNW. 1.3 W. 5 5 
WNW. Ld 2 E. 34 2 
WSW. 2.0 N. ye By 
SSW. 1.3 S. 3 3 























Here again the movements in northwest, southeast, southwest, and northeast direc- 
tions far outnumbered all others. The total movements in these directions is 79 per 
cent. There were many cases of movements in directions slightly oblique to these, but 
tending the same way, which, if included, would swell the total. The southwest direc- 
tion was much more frequent than the northwest, and the movements along southwest- 
northeast lines were much in excess of those at right angles. The west and east shiftings 
were more frequent than those to the north and south. The pieces of furniture moved 
in various ways, tipping over, sliding, and jumping. The movements were often back 
and forth. There is an apparently authentic case of a china closet tipping to the north- 
west, resting at an angle of about 60° against an obstruction, and tipping back 
to its original position. The number of heavy pianos, stoves, and safes which were 
moved is given in the preceding table. Sixty-six per cent of them were moved north- 
west and southeast and southwest and northeast. The evidence is especially good in 
such cases as the sliding of cash registers and scales on smooth counters, which in several 
instances went northwest, southwest, and southeast. The ornamental top of a soda 
fountain, balanced and free to fall any way, fell toward the southwest. 

Experiences and testimony of people. — An earthquake comes and goes so suddenly 
and unexpectedly, and there are so many things to think about, even when one is able 
to formulate any thoughts whatever, that the description by people of the manner in 
which they felt the shock is apt to be only fragmental at best. It is the almost universal 
testimony in the San Mateo region that the first shock was followed by a lull, and that 
this was followed by a renewal of the motion in a different direction. Many state that 
the shock following the momentary lull was the heavier of the two. As to which of 
the two movements along lines northwest-southeast and southwest-northeast came 
first, little evidence has been forthcoming. Persons who agreed in regard to there being 
two successive directions of vibration differed as to which preceded. There were two 
cases of the spilling of liquids noticed by persons, and in both the statement was made 
that the liquid splasht toward the northwest at the first shock. In one of these cases 
the northwest splash was followed by one toward the southeast. A lady who was awake 
when the shock came said that things on the southeast side of the room began falling 
first. A jeweler declared that he was satisfied, from the movement of his pendulums, 
that the main shock was southwest and northeast. Two people were thrown out of bed 
in the same house, one of them being thrown northeast, the other southwest. One of 
these, after getting up, was thrown southeast from a standing position. 

Splashing of liquids. — A form of evidence that could not be influenced by artificial 
position of any kind is that of the splashing of liquids. It is, however, evidence that 
is difficult to get at, partly because the signs of direction are so transient, and partly 
because even when they remain long enough to be seen, they are apt to be either care- 
lessly or not at all observed. The 30 cases of spilling that were considered trustworthy 
and were recorded point to movements northwest-southeast and southwest-northeast. 


DIRECTIONS OF VIBRATORY MOVEMENT. 363 


Table showing directions in which liquids spilt. 




















Direetioul No, of cases Per cent, by 
of spilling. directions. 
NW. ote gee Aca Obs eames NS 6 20 
SW. cee ae, hea eS Ee ee ee 6 20 } 43 
Both NW.-SW. Bee g! Be wine! 1 3 
SP eee ae feted ere Re ULL ne ee 4 14 
Bot Wieser et) Seema oy) Pt! 4 14). 
Both SW.-NE. . 5 eects 
ENE. 1 2 
a ee OS ae or ee 1 lees 
BM Ab iy HTM Wa oe ce oon es 1 >| = 
Both ESE. and WNW. il 3 
OCR ST Sata Oe em, 30 








SW. or NE., or both SW. and NE., 51 p. ct.; NW., or both NW. and SE., 34 p. ct. 


In 20 per cent of the cases the liquid spilt northwest; in 20 per cent southwest; and 
in 3 per cent in both directions, making a total in these two ways of 43 per cent. Four- 
teen per cent spilt northeast, and 31 per cent northwest-southeast and southwest- 
northeast, in combination. This makes a total of 88 per cent in which spilling took 
place along the same lines in which movement in all previous cases predominated. 'The 
rest of the cases of liquids spilling tended the same way, none having gone north or south. 
The water in a reservoir was observed by one man at the time of the shock. He said 
the water seemed to move in waves toward the northeast, and that it splasht high 
on the northeast side of the reservoir. Others declared that waters were calmed by 
the quake. Tanks of water were repeatedly either wholly or partly emptied by the 
splashing of the contents. One lady states that her goldfish were thrown out of a little 
pool with the water, toward the east-northeast and west-northwest. 

Movement of various other bodies. —This paragraph includes all important items of 
evidence that have not found a place in previous sections. It covers cases of falling, 
leaping, and sliding of towers, tanks, porches, pillars, underpinnings, gate-posts, arches, 
roofs, and the pulling apart of walls and partitions, besides the movement of many 
smaller articles. The evidence in most of these cases is especially good. For instance, 
a heavy marble slab on a counter slid lengthwise toward the northwest. A derrick 
which was leaning northeast was thrown toward the southwest. The following are the 
percentages in over 50 such cases: southwest, 35 per cent; northwest, 24 per cent ; 
southeast, 17 per cent; northeast, 11 per cent; a total of 87 per cent for these 4 direc- 
tions, while the other 4 directions, north, south, east, and west, total only 13 per cent 
of the movements. This is more evidence tending to the same conclusion as before; 
namely, that the southwest and northwest movements, and their opposite directions, 
far outnumber all others. In general, things that are thrown or that fall or slide freely 
furnish the best criteria for judgment as to the direction. The above list is largely made 
up of data of this kind. The cases of pulling apart of walls included are very few, for 
in the majority of instances in which parting of walls occurs the action is dependent 
on too many other factors. 

Predominance of northwest and southwest movements. —It has been shown that the 
movements northwest and southwest, and those opposite, greatly exceed in number 
those in all other directions; and there is no question as to the predominance of the 
first two over those opposite to them in almost every case. It is clearest in the move- 
ment on foundations and the splashing of liquids. Evidence in regard to relative amounts 


364 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


of movement in the first-mentioned directions and in those opposite seems to be best 
in the case of foundations, since loose articles may often have been thrown in the direc- 
tion of an earthquake thrust, while houses moved opposite to it. ‘The supposition is 
that houses usually shifted opposite to the thrust. Furthermore, it must be borne in 
mind that the contents of a building may be influenced by the movement of the building, 
rather than by the direct earthquake thrust itself, and thus give results pointing in the 
opposite direction. 

Cause of shifting. — From the fact that northwest and southwest displacements were 
of most frequent occurrence, it seems likely that the main earthquake moyements were 
southeast and northeast. 

The fault which is believed to have caused the earthquake runs in a direction about 
N. 40° W., and passes within 3 miles of San Mateo. It will be noted that the dominant 
directions of movement were parallel and at right angles to the fault-line. 

Evidence appears to show that in any one direction there was a succession of thrusts. 
In one instance, a bureau was jerked by successive small movements a distance of 6 feet 
toward the northwest. The course of such moving objects can often be traced by the 
marks left in dust. Some objects that were moved had returned to their original posi- 
tion when the end of the shock came. 

Relative intensity of the main movement. — Considering only the northeast-southwest 
directions and those at right angles to them, we find that of all the houses that moved 
on their foundations, 31 per cent shifted southwest and northeast, and 27 per cent north- 
west and southeast. (See table on page 359.) 

Of the chimneys that fell obliquely or upward with reference to the slope of the roof 
or that jumped or shifted, which gave the most trustworthy evidence in cases of falling 
chimneys, 22 per cent moved southwest and northeast, and 19 per cent northwest and 
southeast. The figures for all the chimneys give the predominance to movements in 
the northwest and southeast directions, but this fact is not significant, since the majority 
of roofs sloped in those directions. 

Among the cases of liquids spilt, the southwest-northeast movement was greatly 
in excess of that northwest and southeast, 51 per cent of the total spilling in the former 
ways, and 34 per cent in the latter. 

In addition to the evidence of the figures in other tables, that given in the table on 
page 361 may be cited. Forty-seven per cent of the dishes and similar articles went 
southwest and northeast, while 42 per cent went northwest and southeast. The same 
fact is indicated by the dishes that faced in these directions and did not fall.  Fifty- 
eight per cent of the cases in which dishes remained standing on the shelves, when 
they were at liberty to fall in one or more of these ways, were cases in which they 
failed to fall northwest or southeast. According to the table on page 362, in 49 per cent 
of the cases of furniture movement the direction taken was either southwest or north- 
east, or both; whereas it was northwest or southeast in only 30 per cent of such 
cases. 

The following table enumerates the cases in which houses moved a distance of more 
than 0.25 inch on their foundations; in other words, the worst cases of the kind. It 
gives the sum of the distances moved in each direction. 

Among the most serious shifts, those to the southwest predominate slightly in number 
and distance over the northwest ones, but owing to the excess of southeast movements 
over those to the northeast the percentages for the combined opposite movements are 
just the same — 37 per cent in each case. Numerous houses shifted both southwest 
and northwest, but different distances each way. In exactly half of the cases the move- 
ment southwest was greater, and in the other half that of the northwest movement was 
in excess, while the average distance moved either way was the same. 


DIRECTIONS OF VIBRATORY MOVEMENT. 365 


Number of cases in which houses moved measurable distances on their foundations in 
different directions, and average distance moved. 

















Total moved and 
: pa sneer by 
i A N b f A dist direction. Avers list 
cae le crea) caueatony SUSPMT ANI SAP deal atiascs 
Per cent 
of total. 
NW. ol 1.19 
SW. 39 1.05 84 69 11 is 
W. 14 1.36 
NE. 6 1.91 
SE. 14 1.29 29 24 1.39 
E. 9 122 
N. 4 2:37 
S. 5 ‘30 f ? é ee 
Rotaler. 122 1.24 














Southwest-northeast, 45=37 p. ct. of total; northwest-southeast, 45=37 p. ct. of total. 
The entire number moved in first three and opposite directions was 113, or 93 p. et. of total. 


INTENSITIES. 


The houses covered by this study may be grouped in three divisions, according to 
locality: those on the hills at Burlingame and San Mateo heights; those at Belmont, 
Homestead, and San Carlos, which are partly on the level valley land and partly on the 
low hills; and those at San Mateo and Redwood City, on the valley-floor. The data 
indicate strongly that the intensity of the shock was less on the hills than on the flat, 
in spite of the fact that the houses on the hills were nearer the fault-line. In fact, several 
houses on the rock-formed hills very near the earthquake fracture did not give evidence 
of any greater intensity than those at San Mateo. 

The Buri-Buri Ridge, as the hills are called, is composed of an old and very much 
compacted series of sedimentary rocks, sandstone, shale and jasper, and of serpentines. 
Moreover, they are not deeply covered with soil, so that they form a strong foundation 
for the houses. 

The percentage of houses that moved on their foundations on the hills was 6 per cent; 
and at Belmont, etc., 3 per cent moved, as against 27 per cent at San Mateo and Red- 
wood City. ‘This is shown in the table on page 355. Among the very few houses that 
shifted on the hills and in the Belmont region, only 4 or 5 moved an appreciable dis- 
tance, while in a majority of cases in the valley the movement was considerable. 

From the figures given in the table on p. 356 it appears that of the chimneys, 73 per 
cent fell on the hills, 88 per cent in the intermediate settlements, and 92 per cent in the 
valley. The intensity of the shock, as shown by the amounts of falling of dishes and 
cracking of plaster, was greater in the flat country. The following table gives the per- 
centage in these cases. Of course the classification of the damage is very arbitrary 
and the figures at best are but indicative. Of cases recorded in which furniture failed 
to move appreciably in houses, 90 per cent were on the hills. 


Degrees of damage to plaster and household articles on hills and low lands. 





San Mateo AnD REDWOoD. Bretmont HItts, ere, 





AMOUNT OF DAMAGE, 
Slight. | Medium.| Great. | Slight. |Medium.| Great. 





Percentage in cases of crack- 

ing of plaster; °°. ~. 40 30 30 79 11 10 
Percentage in cases of falling 
of dishes, etc., in varying a2 | 














Amount” 9 FL! Sr ke. ets 40 20 40 74.3 23.3 

















366 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


The testimony is good in all cases that structures on the hills suffered less severely 
from the earthquake than those on the plain. If a large amount of similar data could 
be collected on the low, alluvial, often marshy, flat land bordering the bay, it would 
probably be shown that the movement there was still more intense. Houses, however, 
are not frequent there. In low bottom-land there were indications of great intensity, 
and especially in the case of ground artificially filled in. A good example was given by the 
electric railroad track a few miles north of San Mateo, shown in plate 97c, p. It was 
built over the low land on a heavy, but loose, embankment of earth and stone. At one 
place this roadbed was shaken apart between the rails, and a crack from 1 to 2 feet 
wide and extending down many feet, nearly if not quite to the level of the valley, was 
formed in it for a distance of over 1,000 feet. It ran northwest and southeast, parallel 
with the road, and thruout that stretch not one of the heavy steel rails was left unbent. 
One 30-foot rail that was examined had been bent 2 feet horizontally and 10 inches ver- 
tically. Such wrecking of railroad tracks occurred wherever the underlying founda- 
tion was loose, but the stretches of track on solid ground were not affected. The 
low, muddy land along San Francisco Bay, east of San Mateo, was seamed with cracks 
by the earthquake. 


CONCLUSION. 


The following are the main conclusions arrived at in the course of the work: 

1. It is evident that much of the damage to houses, as well as to their contents, could 
be avoided by judicious construction. The disadvantages of certain classes of structure 
should be acknowledged, and search made for more successful styles. Houses prac- 
tically earthquake-proof can be built easily and cheaply. 

2. The dominant directions taken by moving bodies during the course of the earth- 
quake shock were southwest and northwest, with movements northeast and southeast 
only second in number. There appear to have been felt in this region two main thrusts 
or sets of movements that emanated from the fault-line in southeast and northeast 
directions. 

3. The shock was less heavily felt on the hills than on the level land. The lower 
slopes were affected in an intermediate degree. The difference in the two extremes was 
probably almost as much as one degree of intensity in an earthquake table of 10 units. 


DIRECTIONS OF VIBRATORY MOVEMENT, 367 


DIRECTIONS IN THE TOMALES-BOLINAS DISTRICT. 
By G. K. GiuBert. 


The greater number of my notes as to direction of motion pertain to the shifting 
of houses which left their foundations. Most of the houses in this district which were 
thus shifted stood on light, vertical, wooden piers or props, and fell from their props 
in shifting. The direction of falling was so frequently downhill as to show that the 
slope of the ground was an important factor, and this fact leads me to give little weight 
to data of this character. There were, however, a few houses which, resting upon flat, 
unyielding foundations, were shifted horizontally upon these, and their evidence is of 
ereater value. I think also that some weight should be given to the dominant direction 
in which houses of a group were thrown from their supports. 

Other data as to direction are found in the falling of men and animals, and these 
seem to me of value wherever a dominant direction affected a group of individuals. 
The direction of fall of a single individual might readily be conditioned by muscular 
reactions, and thus give little evidence as to the direction of the strongest tremor. 

I am led to question evidence from the shifting of furniture and the throwing down 
of objects on shelves, because in every instance the direction of vibration of a building 
appeared to be controlled partly by its structure. In view of these considerations, 
I regard the greater number of my observations on direction as of little significance, 
and do not report them. 

The clearest data as to direction are at Inverness. While there was much variety 
in the direction of motion of houses at that locality, it was quite clear that the dominant 
direction was westward. This also was the direction toward which 4 out of 5 water- 
tanks were shifted, and it was the direction toward which the mud on the bottom of 
Tomales Bay was moved. The locality is within less than 1 mile of the fault-trace and 
is on the southwest. side. 

At Point Reyes Station, situated 0.25 mile northeast of the fault-trace, the dominant 
direction of shifting was southward, and an exceptionally definite record was made by 
the school-house, which rested on a firm, flat foundation and was slid toward the south. 

At Olema, 2 miles southeast of Point Reyes Station and similarly related to the fault- 
trace, the dominant direction of motion was southwest, or toward the fault, the best 
single instance being that of a pool of water which spilt in that direction. 

At Dipsea Inn, 0.66 mile northeast of the fault, a pier running northeast from the 
spit was wracked toward its outer end. A line of telephone poles crossing the lagoon 
from the end of the pier was slanted in the same northeast direction. In the Inn objects 
were thrown southwest, and of three cottages injured two were shifted or wracked to the 
southwest. On the mainland nearby a part of Mr. Morse’s pier was wracked to the south- 
west. Collectively these facts indicate a dominant vibration to and from a northeast 
direction. 

At Willow Camp, close to the east angle of Bolinas Lagoon and about a mile northeast 
of the fault, several houses moved short distances toward the southeast. 

These various directions are platted in fig. 65. 


DIRECTIONS INDICATED BY MONUMENTS IN CEMETERIES. 


Prof. F. Omori attempted to determine the directions of the earth’s vibrations by a 
statistical study of the thrown monuments in the cemeteries south of San Francisco. 
The results of his investigations are shown graphically in fig. 66, in which it appears 
that the greater number of monuments were thrown in the quadrant between north- 
east and southeast. The mean direction of overthrow is N. 76° E., which is regarded 


368 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


as the direction toward which the greatest horizontal displacement took place due to 
vibration. Other observations on the directions of the vibratory movement may be 
found in Professor Omori’s paper." 














Dipsea 





Willow Camp 


- 
S 
Fic. 65. — Directions of earthquake motion. Fig. 66.— Statistical representation of the directions of fall of monu- 
ments in the cemeteries south of San Francisco. Each x represents 
a monument which fell in the direction indicated by the radius 
on which the x is placed. After Omori. 





‘Preliminary note on the cause of the San Francisco earthquake of April 18, 1906. Bull. Imp 
Bai, Ci aVol lo Nowks 


MARINE PHENOMENA, 


The effect of the earth movement on the sea-level. — In earthquakes along coastal regions 
the waters of the ocean are usually affected, particularly if there be a displacement of 
the sea-bottom. If the displacement has a considerable vertical component, so that 
one portion of the sea-bottom is dropt relatively to an adjacent portion, the ensuing 
displacement of the prism of water over the region affected will generate a periodic wave, 
which will cause the water along the coast to rise and fall with more or less disastrous 
results. If the dropt portion of the sea-bottom is on the landward side of the fault 
upon which the displacement occurs, the wave will be greater for the same amount of 
displacement than if the drop is on the seaward side. If, however, the vertical com- 
ponent of the displacement is quite small, and the movement is chiefly horizontal, as 
in the case of the fault of April 18, 1906, the sea-wave will be correspondingly insignificant. 

The bottom of the Gulf of the Farallones, which was traversed by the fault from 
Bolinas Lagoon to Mussel Rock, comprizes the inner shallower portion of what is known 
as the 100-fathom plateau off the coast of California. This plateau stretches seaward, 
with an average breadth of 22 miles, immediately off the short line of coast from Pigeon 
Point, in latitude 37° 11’, to the mouth of Russian River, in 38° 26’, a distance of about 
80 geographic miles. The area of this part of the plateau is about 2,500 square miles, 
which includes the area of the Gulf of the Farallones, about 1,200 square miles. On it 
lie the Southeast Farallones, the North Farallones, Noonday Rock, and the Cordell 
Bank, having a northwest and southeast bearing thru 30 geographic miles. The line 
projected southeastward strikes Pigeon Point. (See map No. 4.) The summits of 
the Farallones rise as much as 340 feet above the sea; Noonday Rock has 3 fathoms 
of water over it, and the Cordell Bank has 19 fathoms. Inside of these islets there is a 
very. uniform bottom of sand, with a gradually decreasing depth of water toward the 
shore. Outside of the islets the grade of the bottom rapidly increases. The 100-fathom 
line reaches 5 miles to the southwest of the Southeast Farallones; thence it is 10 miles 
to 500 fathoms and 29 miles to 1,728 fathoms. 

There is no means of directly ascertaining the amount of the vertical component of the 
fault of April 18 for those portions of the fault-trace which le on the sea-bottom across 
the Gulf of the Farallones or in the region to the northward. But where it traverses 
the land to the south of Mussel Rock, there is no evidence of vertical displacement ; 
and to the north of Bolinas Bay, while there is evidence of an uplift on the west side of 
the fault, that uplift is sight, not exceeding 1 or 2 feet. The absence of a periodic wave 
at the Golden Gate indicates that the vertical displacement on that segment of the 
fault which crosses the Gulf of the Farallones, if there was any, was very small. While 
there was no periodic wave of the oceanic water generated by the horizontal displace- 
ment of the sea-bottom, there was an interesting disturbance of the level of the sea, 
shown by the tidal gage near Fort Point on the south side of the Golden Gate, which is 
probably to be classed with the secondary phenomena arising from the displacement. 

The tidal gage yields a record known as a marigram, upon which is chronologically 
indicated the rise and fall of the water in the Golden Gate with the incoming and out- 
going of the tide. The record is said to be sensitive to the impact of waves breaking 
upon the bar outside the heads distant some miles from the gage. It is also sensitive 
to the conflicting volumes of water from the north and south parts of the Bay, when 
these are striving for mastery on the fading tide. Former submarine earthquakes in 
distant parts of the Pacific have generated waves which have been recorded on the 

2B 369 


370 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


marigram at the Golden Gate. The marigram near Fort Point, for April 18, 1906, 
shows (fig. 67) a depression of the water-level in the Golden Gate at the time of the 
earthquake, or rather a little subsequent to that event. The amount of the depression 
was slightly in excess of 4 inches. The mari- 

gram shows a blurring of the pencil mark from 

the direct action of the earthquake agitation, 

and this bearing serves to give approximately % 
the time of the shock. It shows that the run- ( 
ning clock of the gage was probably too slow, Ay 
and that the depression of the water-surface 

did not begin instantaneously, but followed after % 
an interval which may have been from 9 to 10 

minutes. Before the shock the gage had had a £ 
small vertical movement, ascribed by the officers 7,8 
of the Coast and Geodetic Survey to an im- Y 
perfect oscillation across the Golden Gate. This | <~ Blurred b 
minor vertical movement continued during the =~ earthquake, 
drop in the level of the water after the shock. if 
The time for the lowering of the water was 
9 minutes, as near as can be read from the 
marigram. It immediately began to recover, 
and the record shows that the water level rose 
without minor oscillations, to the normal level 
within 7 minutes, the total interruption in the 
normal marigram curve due to this depression 
being 16 minutes. After full recovery to normal 
level, the depression was not followed by a com- 
plementary rise of the water-surface, and in 
this sense the movement was not periodic. ‘The 
minor oscillations referred to above ceased when 
the maximum depression was reached, and do 
not appear in their characteristic forms on the 
marigram curve for some hours after. They 
were replaced, however, after 6 o’clock, by 2 or 
3 oscillations having a period of about 40 to 45 
minutes and an amplitude of 1 to 2 inches. 
These probably correspond to oscillations in San 
Francisco Bay. ) 

The Tidal Division of the Coast and Geodetic 
Survey very kindly computed the time which 
would be required for a wave generated at the 
fault-line on the bottom of the Gulf to reach 
Fort Point, and found that it would require 9 
minutes, on the assumption that Fort Point is 
6 statute miles distant from the fault-trace in 
a direction normal to it. The position of the 
gage is, however, 1.3 miles distant from Fort 
Point within the Golden Gate, so that the time 
necessary for the wave to reach the gage would 
be somewhat longer. Now the time at which 
the gage began to fall is between 9 and 10 minutes 





a] 


4sSvog "Sf 94} JO SpIOSaT WHOA “QOGT ‘ST [dy “WV qT OF NW Vyns 


your T ‘Tet 
qnoqe Woy ‘oosPoURIg Ug ‘yUIOg Jog ye WeRIsE —*L9 9 


YUL T ‘TBoyaea :satvog *Laaang dyeposs) puv 


“mmoy T 


-wo0zItoy £400F T 


MARINE PHENOMENA. seal 


after the first interruption and blurring of the record by the shock itself, and this 
coincidence in time suggests that the fall in the water near Fort Point was due to a 
negative oscillation generated at the line of the fault. The effect produced would have 
been brought about had there been a slight drop of the sea-bottom on the outer side of 
the fault. But there is independent evidence, to the north and south of this particular 
segment of the fault, that there was no drop on the west side, so that this explanation 
can not very well be entertained.’ It is also possible that the effect observed might 
have been brought about by a slight expansion of the confines of the Gulf of the Faral- 
lones, due to the differential movement along the fault, but this would not explain the 
coincidence in time. The period of the east-west oscillation of the waters in the Bay 
of San Francisco, between West Berkeley and Fort Point, has also been computed by 
the Tidal Division of the Coast and Geodetic Survey to be about 40 minutes. This 
agrees fairly well with the two or three oscillations recorded by the gage after 6 o’clock, 
and indicates that the drop of the water-surface outside of the Golden Gate generated 
an east and west oscillation in the Bay of San Francisco. 

Tidal observations conducted at Fort Point for a period of 1 year from the date of 
the earthquake indicate that there was no change of the relative altitude of sea and 
land at that point, as compared with the conditions prevailing during the 3 years pre- 
ceding. A review of the observations for the past 9 years, by the Coast and Geodetic 
Survey, reveals, however, the interesting fact that in that period of time there has been 
an apparent subsidence of the coast at that point of 4.8 inches, practically all of this 
having been accomplished in the first 6 years of this period. There has been no move- 
ment in the last 3 years. (April 18, 1907.) The only other tidal gage maintained on 
the coast of California is that at San Diego, and the marigram obtained there shows 
no abnormal movement of the surface of the sea referable to the earthquake. 

The only other report indicating that the level of the ocean was affected along the 
coast is by W. W. Fairbanks, of Point Arena, who says: ‘I have endeavored to learn 
of any unusual action of water along the sea-coast, and can relate but one instance of 
anything approaching the character of a tidal wave. On the day of the shock I traveled 
by wheel and on foot from Albion to Point Arena, 25 miles. At the mouth of Navarro 
River, at 8 o’clock on the morning of the 18th, I learned from reliable sources that a 
section of about 10 acres of low, flat land about the mouth of this river was entirely 
submerged for some minutes immediately after the shock.” 

The shock felt by ships. — Information regarding the perception of the shock on ships 
at sea or in harbors has been collected by Prof. George Davidson, and the following 
notes are chiefly the result of his inquiries: 

The U.S. T. S. Pensacola, moored to the pier at the U. 8. Naval Training Station, 
Yerba Buena Island, San Francisco Bay, felt the shock on the morning of April 18, 1906. 
Surgeon L. W. Curtis reports that while in bed on the Pensacola he felt a vibratory shock 
lasting about 30 seconds, with one heavy jar about the middle period of the shock. A 
gentle rumbling sound coincided with the shock. The phenomenon closely resembled 
vibrations which are at times set up in the ship’s hull on starting the dynamo, and it was 
mistaken for that, tho much more active and exaggerated than ever before observed. 
The vibration shook down some loosely piled books and papers from a table. 





1 This explanation is, however, advocated by Prof. H. F. Reid. In a note received while these pages 
are in proof he says: “ If a depression occurred on the western side of the fault-line, extending for some 
distance to the westward, it would start a wave of depression towards the Golden Gate which would take 
9 minutes to reach Fort Point and this is just about the time recorded by the gage. The time necessary 
for the recovery to normal level would depend upon the extent of the area depressed. If this were a 
narrow block, a wave of elevation would follow quickly upon the wave of depression and we should have 
a rapid elevation of the tide-gage above its normal position. As no such wave appeared and recov- 
ery was very gradual we must suppose that the deprest area extends for some distance to the west- 
ward, so that the recovery was slow. This is the only explanation so far offered, that would produce 
the effects observed.” 


3i2 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 

The pilot-boat Gracie S. was lying in 18 fathoms of water near the lightship off the 
San Francisco Bar. She was suddenly struck by a seaquake which caused her to quiver 
as if the chain were running out of the hawser pipe. When the pilot boarded the German 
Cosmos steamship Nyada, the captain reported that his vessel had been shaken as if 
she had struck on rocks. The pilot-boat Pathfinder was lying in the vicinity, in 20 
fathoms, and reported the same effect. 

The steam collier Wellington, inward bound, between Fort Point and Point Diablo, 
in 50 or 60 fathoms, reported that the vessel was struck as if she were upon rocks. (Per- 
sonal report of Captain Hayes, of the Board of Pilots.) 

The steamer Alliance, off Cape Mendocino, reported by Mr. H. H. Buhne, of Eureka: 
The captain said she was struck a hard blow, as if she had run on a rock at full speed; 
time, 5° 11". Mr. Buhne states that all ships in the harbor at Eureka felt the quake, 
but in South Bay it was heaviest. One vessel was hurled against the wharf time and 
again, throwing down piles of lumber and shingles. 

The schooner John A. Campbell felt the shock at sea, off Point Reyes. The following 
is a memorandum of the event by Capt. C. J. 8. Svenson: ‘Ship’s local apparent time 
April 18, 1906, 5" 15" a.m. Lat. 38° 00’ N. Long. 126° 06’ W.; 145 miles true west of 
Point Reyes. W eather fine; sky clear; wind fresh from north- northwest: sea moderate ; 
ship’s course southeast; speed 7 miles per hour. The shock felt as if the vessel struck 
lightly forward and then appeared to drag over soft ground, and when aft a slight tremor 
was felt; the whole lasting only a few seconds.” The depth of water in the vicinity of 
the ship’s position is 2,400 fathoms. 

The steamship National City was approximately in lat. 38° 24’ N. and long. 123° 57’ 
W,; 29 geographical miles distant from the nearest point on shore and about 31 miles 
from the fault-trace along the valley of the Gualala River. The vessel felt the shock 

t 5° 03" a. m., April 18, 1906, ship’s time. James Denny, the chief engineer, supplies 
the following comment: ‘The ship seemed to jump out of the water; the engines raced 
fearfully, as though the shaft or wheel had gone; then came a violent trembling fore 
and aft and sideways, like running at full speed against a wall of ice. The expression 
‘a wall of ice’ is derived from my experiences in the Arctic.’ In this vicinity the chart 
has several soundings, as follows: 911 fathoms over clay and mud at 11.5 miles on the 
line to Gualala Point; 1,586 fathoms over clay and ooze 8 miles north by compass; 
1,821 fathoms over clay and ooze 14 miles N. 54° W. by compass. 

The wharfinger at Santa Cruz reports that he heard a rumble before the shock, coming 
from the southeast, and saw the seismic wave traveling shoreward, causing a great rattling 
and crashing when it struck the town. Two distinct sets of vibration were felt, the latter 
being the harder. There was very little surf, the water looking like that in a tub when 
jarred. The wharf, extending southeast, s pocried to pitch lengthwise. A steamer between 
Santa Cruz and Monterey; alan one at Monterey wharf, ale the shock; it jarred them as 
if they had struck bottom. 

Shocks felt at sea subsequent to April 18, 1906. — The ship Alex Gibson, at 7" 05™ P.M. 
August 3, 1906, when in lat. 25° 35’ N., long. 110° 06’ W., experienced a tremendously 
heavy seaquake, lasting about 40 seconds and shaking the ship from stem to stern as 
if she were bumping over a ledge of rocks. It shook tools out of the racks in the ecar- 
penter shop; threw pots and pans down in the galley, cups and pitchers from hooks in 
the pantry, and all lamp glasses off the lamps. The crew came running aft not knowing 
what was the matter, and the captain thought the yards were coming down. The sea 
at the time was perfectly smooth, the wind light from the southwest, no land in sight, 
and all sail set in fine, clear weather. At 7" 10" p. m., ship’s time, another light shock 
was felt, of about 15 seconds duration; and from 8 to 12 midnight two more very light 
shocks were felt, but the time was not noted. The captain states that he had experienced 


MARINE PHENOMENA. oie 


an earthquake at sea on a former occasion, but the one felt before was nothing compared 
to this one, either in force or duration. (Hydrographic Bureau.) 

The bark St. James, Capt. F. O. Parker, while in lat. 26° 19’ N., long. 110° 25’ W., in 
the Gulf of California, on August 26, 1906, was shaken by a seaquake at 122052) 
The shock lasted a minute, and the sensation was as if the vessel were striking upon 
sunken rocks. Upon arrival at Guaymas, the captain learned that no shock had been 
experienced at or about the time noted. (San Francisco Chronicle, Sept. 16, 1906.) 

The bark Agate, Capt. C. H. McLeod, while off the northwest coast in lat. 43° 10’ N., 
long. 128° 50’ W., 100 miles west of Coos Bay, experienced a heavy shock on September 
2, 1906, at 3°45" a.m. The shock lasted nearly 1 minute. The sensation was as if the 
vessel had struck a coral reef or rock. The wind was light, the weather clear, and the 
sea smooth. At 3" 55" a.m., another shock was felt, not so severe nor so prolonged as 
the first. (San Francisco Chronicle, Oct. 2 and 9, 1906. Hydrographic Bureau.) 

The ship Robert Searles, Capt. J. H. Piltz, while in lat. 41° 78’ N., long. 125° 52’ W., 
85 miles northwest of Cape Mendocino, experienced a severe shock on September 14, 
1906, which occasioned a panic among the crew. The cargo (lumber) and upper works of 
the vessel were shaken. The shock lasted 25 seconds. (San Francisco Chronicle, Sept. 17, 
1906. Hydrographic Bureau.) 

The American schooner Stanley, Capt. K. Petersen, while in the calm center of a 
cyclone, in lat. 46° 09’ N., long. 125° 22’ W., 55 miles west of Cape Disappointment, on 
November 6, 1906, felt a sharp shock that lasted 2 or 3 seconds. Immediately after- 
wards, when looking toward the southwest, the captain saw 3 mountainous waves com- 
ing; when they struck, the ship began to pitch and roll violently, and he thought every 
minute she would be swamped. (Hydrographic Bureau.) 

The schooner Melrose, Capt. M. McCarron, while in lat. 37° 35’ N., long. 123° 35’ W., 
felt a seaquake on February 3, 1907. The first shock was at 10" 30” A.., lasting about 
8 seconds; and the second at 10" 50" a.m., lasting about 5 seconds. Neither shock 
was violent, but each caused a decided trembling of the vessel. The motion was from 
east to west. The sky was overcast and the sea was smooth, with light westerly winds. 
The position of the vessel was 28 geographical miles S. 73° W. from the Southeast Faral- 
lon. The nearest sounding on the chart is 5 miles north of this position, where there 
is shown 1,726 fathoms of water. 


NUMBER OF MAXIMA IN THE MAIN SHOCK. 


In response to various circulars sent out by the Commission, and to direct inquiries 
by the members of the Commission or their aides in the field, 154 replies have been re- 
ceived, which constitute testimony as to whether the main shock comprized one or more 
maxima. Many of these replies are rather questionable scientific evidence, inasmuch 
as many of them were in response to a leading and suggestive question, and very few 
of them have been subjected to the clarifying process of cross-examination. So few 
people were awake at the time the shock began that but a small proportion of the replies 
come from people who were in full possession of their observational faculties at the begin- 
ning of the disturbance; and of those who were suddenly and rudely awakened, few were 
sufficiently alert for deliberate perception at the time and had to rely upon a somewhat 
confused memory for the character of the shock. Yet the testimony is of value, and 
indicates a very general consensus of the impression that there were 2 principal maxima 
in the shock; and the failure of many to recognize or remember 2 parts to the shock 
does not seriously invalidate the testimony of those who received that impression. 

Of the 154 replies received, 98 testify to 2 maxima; 46 to but one maximum; 9 to 
3 or more maxima; and 1 to more than one. Of the 98 who reported 2 maxima, 67 
discriminated between the 2 parts of the shock, as to their relative intensity; and of 
these 67, there were 48 who had the impression that the second maximum was the more 
severe, and 19 who thought it the less severe. Of the 46 who recognized only one maxi- 
mum, 32 were beyond the zone of destructive effects, where the intensity was VI or less 
(in a few cases VII); and of the remaining 14 cases within the zone of destructive effects, 
11 were offset or contradicted by other reporters in the same general district as them- 
selves, who record two maxima. It would thus appear that within the zone of destruc- 
tive effects, say out to isoseismal VII, the evidence, such as it is, points unmistakably 
to the occurrence of 2 maxima; and the prevailing opinion is that the second was 
the stronger. The failure on the part of many reporters to discriminate 2 parts of the 
shock beyond the isoseismal VII is not surprising, and is offset by the considerable num- 
ber of reports in which 2 maxima were noticed. 


List of observations as to the number of maxima in the earthquake shock. 





No, of 








soureka- seo coe 


| Portuna eeeseeee = 


Pepperwood ....-- 
Briceland see see ee 


| Fort Brace... 
| Cilen Blair scot... 


Albion. oes. a eee 
Philo. shee. eee 
Kish Rock 225-222 
Annapolis. ---22-- 
HortiuRossieee. eee 
Cazadero 222 - eee 
Hemlocksenee see 


Lakeportio-2- se ae 


Sanhedrin cee 


Veteran’s Home .. 
Wooden Valley ... 


Cotati css 2ecimens 





AM Hs Bell Seeeee se 
D. L. Thornberry - 
JH elie. saree 
J. W. Bowden .... 
Ha Huesing > s)-ce. 
AE ocObtise see 


Ga Wa Call esaee= 
K. H. L. Cowley .. 
Ce DAL Bowens 
M. C. Bale 


ASBrownee snes ee 
H. W. Chapman .. 
Ce cL Jenrey occas 





o74 


\ 
NWNeRRENW NNN RR NR ebb 





~ 


b 


Several 


Several 


BNF NRe 





Maximum intensity toward end; duration 47s. 


Locality. Reporter. Maisaa. Remarks. 
| Nolton of s- ce. seee Clara Ward....... Second stronger. 
| Crescent City ..... (x: Sartwell. 22-22. Interval about 2 seconds. 
Montague ..-....- C. H. Chambers -. Duration 30 seconds. 
io ton Stemerme eee Ge LDIsOl eee er 
BiowBargoeeee ee W. A. Pattison ... A tremor which eased up, then another stronger. 
VP ODOOSC -.ee een C. B. Lakemore... 


One greater than the other. 


Second stronger. 
Second stronger. 


Continuous shock, 40s., ending withh eavy one. 


About the same intensity. 


Second stronger. 


lirst in wave motion; second rotatory. 
Increased in force up to third or fourth. 


Second stronger. 
Second stronger. 


Oscillatory, ending with series of shocks. 


Second stronger. 
Second stronger. 


First stronger. 








NUMBER OF MAXIMA IN THE MAIN SHOCK. 


List of observations as to the number of maxima in the earthquake shock — Continued. 


Locality. 





Tamalpais... . «-- 
San Rafael 


Mountain View ... 
Woodsidei.... 0... 





Ome ces ote 


Campbell ......... 


do 


DEVI ANG coe ree wie sie 


IPARIGEITES Sei. sales oe 

(4 miles SW.) .. 
Bear Valley 
Bitterwater....... 
Hernandez 
Mt. Hamilton..... 


es 


Calaveras Valley - . 
Livermore ......-- 
am yall@c even «+ << 
Mimliden 2282... - 
Mills College ....-- 
Berkeley 


TGS: cS 3256 
Parallones.. ...... 
Santa Cruz Range 


Bellvale 
Santa Cruz 


Delmas ’ 
Seabright ¢...-- 
Twin Lakes j 
Bonnie Doon 
Soquel 220: see 1. = 


Salinas 
Monterey 22 .--- 2 
Chualar 
onoak. 22 ee see 


eet te eee eee 


Shandome ces. cose 








Reporter. 


No. of 
Maxima. 





. 


Remarks. 





J. J. Lindunger... 
W. W. Thomas -.. 
EY Reuboldss-2e- 
Re Landonse ese 
x. L. Richardson . 
F. M. Watson .... 
J. Ds Bennett =. -- 
B. A. Peckham ... 


cn Gee tlartzelloasse 
M. Connell 


J. 8. Ricard 
F. M. Righter .... 
F. H. McCullogh.. 
J. H. Snyder 


Wiese Lessin eines 


weet eee 


eee eee 


T. Wightman....:. 
J. F. Tathan 
Mrs. A. L. Sears .. 
Flora E. Beecher . 
W. J. Lawler 
We Bestuart 2.26 


eee eee eee eee 


(oO pepe an ey 
Ca Z eon ees 
BB. M. “Tucker: . 2. 
He Ke Palnveres se 
A. M. Hobe 
W. W. Campbell. . 
Ry Ingleson?.= ...- 


WeGallyaae ee 
J. Keep 
A. CoLawson~-2.< 


J. G. Peter 
JeAly Boyle. a. 
Mea Doyle te. ess. «- 


Dilla iepell see. 
GavAl Warine 2. 
O. J. Lineoln 


GaeAa WW airings sere 


Tie ha lha vers... 5. 
Matilda Baker ..-. 
D. R. Guichard... 
E. McCabe 
Gea Waring. .-5- 
H: H.. McIntyre =: 
Bertha M. Abbott 
INEOW). dames] se oe 
G. P. Anderson... 
JeRRISt 








WNNMNMN bb bo 


bo e bo bo me bo bo bo bo 


bo 


SF NWWNWNRehe 


NRFNWNNWNNNNNNW 


bo bo bo 


bo bo bo 


bo 


RPbNwNWNReR bw bo 


bo 








Increase in severity in latter half. 
If any difference, first stronger. 
First light and long, second hard and short. 


First light, second heavier. 

First heavier. 

First lighter and longer than second. 

First heavier. 

First and second were heavy wavy motions; 
third was short rapid trembling. 

Two main thrusts or sets of movements. 

Second stronger. 

Personally observed but 1; others observed 2 or 
3 and there is a general agreement that second 
was stronger. 

Second more intense. 

Came suddenly, explosion-like, then a violent 
swaying. 

Two shocks, then finally a twist and an uplift. 

Second stronger. 

Wife noticed a preliminary shaking. 

Partial intermission of 1 or 2s. Second much 
stronger. 

Interval was not sufficient to allow moving ob- 
jects to come to rest. 


Second stronger. 

Followed by tremors. 

About equal. 

Second stronger. 

First stronger. 

Almost continuous; second did most damage. 


Noted by several people. 

Second stronger. 

First part genitle, second more severe. 
First harder; memory uncertain. 

Jar, then pause, then tremble. 

First harder. 

2 separate shocks. 


Second stronger. 
First sideways, second upward. 


First prolonged, with secondary maxima; second 
brought déwn chimneys and ended rather 
abruptly. 

Second stronger. 

First stronger. 

Tremor, then distinet shock; then violent shock, 
then tremor. 

Continuous shake with 2 heavy parts. 

Second stronger. 


Shock came suddenly, diminished, then at a 
second jolt the chimneys fell. 


Second stronger. 
First stronger. 
Second stronger. 


Felt as 1 continuous vibration. 
Second stronger. 

Second stronger. 

First stronger. 


Continuous shock, light at first; finishing with a 
hard stroke and twist. 











376 


REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


List of observations as to the number of maxima in the earthquake shock — Continued. 








Locality. 


Reporter. 





San Luis Obispo... 
AO ee eee 


Santa Maria ...... 
Pismo 
Lompoc 

elo Me Peabo 


Los Angeles 
Compton 
Azusa 
Tolicaipace eee 
Redding eeeess.——" 
Colusa. Seana 


Meridian 
Marysville .......- 
Rumsey. .e-e-eee 
Guindaseerees-eee 
Capay reece 





Plainteldee-see ce 
Black’s Station ... 
Knight’s Landing . 
Sacramento......- 


Bairoakss oe. eee 
Maim Prairie .<.--- 
Binghamton ...... 
Collinsville. 22 -..-- 
Ione 


Oakdale .......... 


Westley:-S2eeees se 
Merced 
Madera2e eee eee 
Fresno 


Kingsbury 52-2 .A20 
Riverdale........- 
Visalia 
Exter 

Bakersfield 
MoArt hureee oes 
Susanville 
Quincy ase 
Kiittlewee eee 
Beekwith Se. ssee" 





Boca 
Stirling City .o2. <- 
Paradisces= eae 
Allegheny 
Pino Grande...... 
Nashvilleae eee 
West: Point soos 
Railroad Flat ..... 
Milton ese 
Tuolumne 

Fo (Ne aii Se ye) Sar 
LaGrangés..- 9s. - 
Sequoia 
Darrah 


Golde: Societe ce: 
Magnet.....e. 3 ence 


oOo neve 
Lone Pines ese ees 
OOM eS treats, 4 Foe 





S-DeBallowsesce- 
Jiekt. wy Lams eee 
M. R. Venable.... 


F. R. Schanck ..-. 
Emma M. Patchett 
A. MeLean 


J. A. Dodge 
S. F. Hunt 
We Da 
L. A. Rockwell ... 
A PaGriththeecese 
. C. Meddington 
L. F.. Bassett. 22: 


2. delay lots. sass 


S. Schwale 5.2:..- 
I. A. Morris 
H. O. Purington .. 
S. P. Cutler 
DoT. Shampyeasss 
J. Av Marshal. 


L. M. Shelton .... 
Mrs. A. Rattike... 
We HisSimitheesee 
Ja Antonini sc..." 
J. F. Scott 
Baba Higby. eee 
E.G. Crawiord...< 
Je la SLO Wie 


J.P Bolton: ae 
W. J. Williams ... 
AS Be Woomiseeees 
W.. Lensoneses-— 
Aa Ms DGitiys. ees 
H. R. Stephens ... 
A. G. Grant 
JMeArthuree = 2 
J Pranic pe eee 
i A wBarretineere 
F. Campbell ...... 
J. W. Middleton .. 


A. BE. Daswell .... 
H. B. Weaver ...- 
eWay sce 
W. A. Clayton.... 
W. E. Basham.... 
Jes Fleal da. 


Layo eee 
J. H. Southwick .. 
J.T. Thompson .. 
JeebmdUOO eT eae. 
J. A. Hammond .. 
M. Crocker 


T. J. Rhodes 
? 


EK. A. Benedict ee 
G. D. Louderback 


Gah Marchese 





No. of 











Masinae Remarks. 

1 

1 50 seconds long. 

2 Slight tremor; then a second more severe; then 
a distinct oscillation, quite hard; then a tremor. 

3 First and second, 1 or 2s.; third, 12 to 15s. 

2 Second stronger. 

1 One long shock. 

2 First gradually increased to maximum and 
gradually decreased. Second died suddenly. 

1 About a minute long. 

3 Second strongest. 

1 

2 First stronger. 

1 As if house had been struck by heavy blow. 

=F 

1 

More | Shock would die out, only to return again. 
than 1 
2 Second stronger. 


NOWNNWNRRK WW 


NEE REN EN EN ENN NNNHEWNHN RNR 


NNWNNRFNRFNNN ENN RR ee NRe 





First lasted about 45 s.; the second about 90. 

Second stronger. 

Continuous shake. 

Continuous shake. 

First stronger. 

First stronger. 

First stronger. 

First stronger. 

Oscillation ended in 2 jars, with appreciable time 
between. 

One straight shake, very light. 


Second stronger. 
Second stronger. 
Second stronger. 
Of equal strength; interval of a few seconds. 
Second stronger. 


Second stronger. 

Second stronger. 

30 s. and 60 s.; second stronger. 
First stronger. 


Second stronger. 

Last most pronounced. 
Nearly equal in intensity. 
10 seconds. 

First stronger. 

Probably 2 s. 


Not sure; there was a wavelike motion, with a 
sudden jar at the end. 
60 s. 


Second stronger. 


Second stronger. 


Second stronger. 
2 prolonged light shocks. 
Second stronger. 


Both about the same; quite heavy. 


First stronger. 
First gentle rocking; second small jerks. 
A few seconds apart. 
First stronger. 








SOUNDS CONNECTED WITH THE EARTHQUAKE, 


An interesting manifestation of the earthquake was the sound which was heard by 
many people in connection with the shock. Appended is a tabulated statement of the 
testimony bearing upon this phenomenon, if it may be so called. In this tabulation 
there are recorded 81 observations of people who heard sounds, without segregating 
those which are reported in a summary way as the common experience of ‘‘some,” 
“several,” or “many” persons. Of these, 40 report having heard sounds before having 
felt the shock; 14 report the sound as accompanying the shock or coincident with it ; 
3 heard a sound after the shock; and 19 report having heard unusual sounds at the 
time of the earthquake, without further specification. Besides this, there are 3 reports 
of sounds having preceded after-shocks, one case where the sound was observed to pre- 
cede the second phase of the shock but not the first, and one case where sound was heard 
but no shock was felt. The observations are fairly well distributed over the region 
affected by the shock. Besides these observations of a positive kind, there were many 
cases reported where no sound was heard, altho the people were awake. 

In view of the 40 positive and independent observations of sounds having preceded 
the shock, with, in some instances, specific evidence of actions induced by the sound 
having been engaged in during the interval between first hearing the sound and feeling 
the shock, there can be little question that sound vibrations of the air actually preceded 
the sensible shock. The testimony of the 14 persons who heard the sound during the 
shock does not contravene that of the 40 who heard it before, nor does that of the 19 
persons who do not particularly specify the time relation of the sound to the shock. 
Sounds heard before the shock may well have continued thru the shock and come to the 
attention of less alert people only when the shock was felt. The three observations of 
sounds preceding the after-shocks are corroborative of the 40 referring to the main shock. 
The one case near Alturas, where men in camp heard a sound but felt no shock, is an 
interesting and exceptional, but credible, one. 

The evidence as to the character of the sounds is consistent and uniform. They 
were vibrations low in the scale. This fact suggests an explanation of the failure of 
certain people to hear the sounds when others in the same vicinity observed them. It 
may be that the vibrations in question are below the range of audibility of some people 
and within that of others. With this question in mind, an inquiry was addrest to Prof. 
G. M. Stratton of Johns Hopkins University, in regard to the limit of sound. His reply 
was as follows: 


The lowest limit of sound is so differently given by different investigators that it seems 
clear that individual differences play an important part. The limit is placed all the way 
from 8 to 30 double vibrations a second, and that may represent the range of personal 
variation; but more probably it varies between 16 and 30; and those who think they 
hear as low as 8 are in reality hearing the second partial of that tone, viz.,16d.v. This, 
of course, applies only to the perception of tone; for of repeated shocks at a very low rate 
we can still hear the separate shocks, e.g., puffs or blows, but they do not as yet fuse into 
a continuous tone.! 


Now if it should be a fact that the rumbling sounds which preceded the shock fall 
within the range of from 16 to 30 double vibrations per second, then from the probability 
set forth by Professor Stratton, the auditory organs of some people would be sensitive 
to such vibrations, while those of others would not. 





+ Professor Stratton refers to a chapter on ‘‘Tiefe und Tiefste Téne,” in Helmholtz’s Lehre von der 
Tonempfindungen, where the difficulties of accurate determination and the different things that appear 
in such tones are well set forth, 

377 


378 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


Another interesting question to which the testimony gives rise is: How do such vibra- 
tions reach any locality in advance of the shock? The seismic waves traverse the earth’s 
crust very much more swiftly than sound-waves do the air, so that it is a physical impos- 
sibility for sound-waves generated in the air above the seat of disturbance to outreach 
them. The vibrations observed as sounds must, therefore, be transmitted to the at- 
mosphere by tremors of the ground which precede the larger waves, and which are not 
otherwise perceptible to the senses ordinarily. These doubtless correspond to those 
phases of seismic movements which are recorded by delicate instruments and are known 
as ‘preliminary tremors.” 


Noises heard at the time of the shock. 















































Locality. Reporter. Observer. Kind, direction, time of noise, ete. 





Ferndale.......- AS WiablackburngiSamen.ss. soe Accompanying the quake was a rumbling, 
roaring sound. 
COVelot tress E. 8. Larsen .... | Large proportion | Roar just preceding earthquake shock. 
of residents.... 
Fort Bragg......+ O. Fa Barth....- AMS. sae ees The wave traveled SW. and a roar ac- 
companied it. 
Mendocino ...... Wm. Mullen..... SaMe sac. de. fee Unusual rumbling sound like distant thun- 


der, preceding shake, being loudest at 
commencement of disturbance. 





Albionger een ee Ji CoVIGraniss ans aI Oia is/o ete tele Roaring noise like heavy fall of hail com- 
ing from ocean to the west. 
Point Arena..... W. W. Fairbanks | Not named...... Heavy roaring sound preceded the shock. 
Point Arena Light- dO. Ave a. Keeper.ssssceecee Blow came quick and heavy, accompa- 
NOUSG@2 neater ae nied by heavy report. 
Upper Lake..... C. M. Hammond A roaring noise past off to SW. 
GO tes ce eee ire CO ieee Workmen. «. 3.5... A noise in the trees as tho heavy wind 


were blowing thru them; then the 
rumbling past off to SW. 











Cloverdale ...... M.C. Balew.2.6 Many persons.... | Rumblings before the shock. 
Healdsburg.....- HaRe Ball se ser DAME: . sie ceisectss Attended by great rumbling noise, as 
thunder. 
Santa Rosa.....- Miss F. Locke... | R. Worthington... | Heard roaring. 
GO neemesee ss GO ween sere. Mr. Campbell.... | Heard a great roaring 2s. or 3 s. before 
the shock. 
Ose we isha eee QOgee: axe ox Watchman ...... Heard noise in SW.; then felt breeze; then 
felt shock. 
GO sen eee ete O27 sence Mrsmliloy dresses Heard noise; ran to window and opened 
it; then shock came. 
OO serietetse eats eleMi Sareea PAR TOVG eee eee ers Heard roaring and saw wave of earth 2 
y feet high. 
Cotati. Of Ly Jefireyxexe |: Samersoe ee ee Sound as of a strong wind before shock. 
TOMBS: seams Oss een sy AS DON. ss seer Heard roaring and said, ‘Oh, there’s 
thunder,’’ before the shock. 
(6 (65 eS rs GOs Saas es} Adfarmer’. seeseee Heard roar from SW. 
MOGs < cewek BOnt eis woe Mr, Scoudye. 2 -er Heard a great roaring sound from SE. 
Point Reyes Sta- GO seesi eters AU Taner pecs see Heard roar, then felt wind on my face. 
HON Sos. 2s 
Olemiar. fess see dO. eee A dairyman ..... Heard noise in the ground, got up, then 
felt shock. 
Bolinas! en eee Ky Haston.c so. = SAMs zo sue bee Rumbling noise preceded one after-shock 
on April 18. 
Calistoga. = -cc-- Dan Patten ....- ATE. =o Ss coe See A rushing noise before shock came. 
Napa ficteoee ton he Ell See Not named ...... A rumbling, then came shock. 
FALCULAS Beton octet GuBetowle 2.2. Somemenincamp | Heard low sound of earthquake, but did 
not feel shock. 
Redding 22-1 sis Li. FS Basset... - DIALOG oe eee iets ee Noise resembled a passing train; it pre- 
ceded and outlasted the shock. 
ChICO @)An-eeee nie E. Mayhew....-.. Same. 22s eeemee Rumbling sound thruout the disturbance 
like heavy-laden wagon passing house. 
Willows......... A. Ws Sehornwsc. PSamecresevtry ce Unusual rumbling sound preceded shock, 
gradually grew louder, and died away 
with the shaking. 
Colusa f.c2. aces Fred Roche..... Names. .ceee oes Sound like an approaching train coincided 
with shock. 
Berkeley........ Miss F. Locke... | Capt. ire Dept... | Was awakened by roar 5 s. before shock. 
San Francisco... | M. C. Erskine... | Same...........- Awake at 5" 10" a.m. Heard a great 
roaring from NE.; soon the shock came 
from same direction. 

















SOUNDS CONNECTED WITH THE EARTHQUAKE. 


379 


Noises heard at the time of the shock. — Continued. 





Locality. 


Reporter. 


Observer. 


Kind, direction, time of noise, ete. 





San Francisco... 


Peninsula of San 
Francisco ..... 


San Mateo 


San Jose 


a 


Santa Clara...... 
(3 mi. west) 
Congress Springs 





MUnull OL coe. oo 


Scott Valley (San- 
ta Cruz County) 
Santa Cruz...... 


HOWMGC hes. eles. 
Wilder’s Dairy 
N. W. of Santa 
AO TIDZ ee Ss bo Te 


HOUSE. Se oo an 


eee eee 


San Luis Obispo, 
1 mile east of.. 
New Almaden (Ha- 

cienda) 
Seyotes ..)..6Pae. 


Gilroy to Hollister 


Tres Pinos 


Bell’s Station... . 
Paicenes 





Mt. Hamilton ... 
Calaveras Valley 


Modesto. --.- o- 


AR AL, ASG cis. 


R. Anderson ...- 


B. A. Peckham.. 
Mr. Connell ..... 
WS. Prosser’ =e: 
Tera say depress: 
J.C. Branner.... 
Ike Wek Siyere see 
W.S. T. Smith. . 


F. H. McCullogh 


L. E. Davidson.. 
Miss F. Locke... 


es 


G. F. Zoffman... 
G. A. Waring.... 


Kee surtige toes 
G. F. Zoffman... 
E. Hughes 








Lieut. Bertholf and 
other officers ... 
Many persons.... 


Mr. Maxwell..... 
SamMes se. 4ee eae 
Several good ob- 


servers outdoors 
D: Piekering..2., 





Residents:2-s...- 


Mia Wiamciaenee ee 
Same let ate 





Different persons 
Mrs. Field 


Wharfinger 
keeper 


Not named 


Kegper sow. setae 
Some people..... 
Not named 


SPaMmeseee ny sce ce 


sete ee 





eee ee 





R. Ingleson ...... 


Several persons .. 


Green Bros:a.s.e 





Bir, Eisey c<eose¢ 


A low rumbling preceded earthquake. 


Noise accompanying the shock; inde- 
scribable noise associated with main | 
shock; immediately after the shock. 

Heavy rumbling which he took for thun- 
der, from NW., before shock. 

An undertone, rumbling sound coincided 
with beginning of shock. 

The noise of the quake came from SE. 
and died away toward San Francisco. 

Sound compared to stampede of cattle. 





Shock accompanied by rumbling; after- 
shocks preceded by sound like a blast. 

Premonitory roar came from south. 

No sound heard for main shock, but 
muffled sound heard just before each 
minor shock. 

Sound as of bad storm coincident with 
first and worst of shock. Later in 
the day there was a rumbling sound to 
me (deaf) not unlike a distant detona- 
tion. 

Attention first drawn to a slight rum- 
bling noise. 

After every shock on April 18 was a rumble 
like that of artillery. 

Tremendous roaring in NE. 


Rumble before shock. 

Noise as of a wagon crossing a bridge pre- 
ceded every quake. 

Shock preceded by rumbling from south. 


Distinct noise as of team crossing a 
bridge to NW. preceded every shock. 
Distinct rumbling preceded shock. 


Noise as of wind preceded the shock. 

Shock described as beginning like a sub- 
terranean blast. 

Rumbling noise coincided with shock. 

Sound reported to have been heard. 

Noise heard after shock. 

Great roar heard. 


Loud noise like thunder traveled north- 
ward, distinctly preceding shock. 

Noise from SE. seemed to pass over him, 

Heard roar, horse became frightened 
before shock came. 

Rumble heard all thru region from Old 
vilroy and San Filipe to Hollister. One 
said from SE., another from SW. 

Distinct rumble preceded shock at Palm- 
tag’s winery. 

Rumble distinctly heard before the shock. 

Distinct noise preceded shock at Cienega 
Lime Kilns. 

No noise before quake, but report as of 
blast immediately preceded second 
(hardest) period of vibration. 

Sound as of flight of birds simultaneous 
with shock. 

The two separate shocks accompanied by 
roaring sound from north. 

Roaring or rumbling sound beginning a 
few seconds before and continuing until 
end of disturbance. 

Roaring sound just before shock. 

Rumbling sound. 




















380 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
Noises heard at the time of the shock — Continued. 
Locality. Reporter. Observer. Kind, direction, time of noise, ete. 
Modesto....... KE. Hughes... | A. H. Holtman... | Shock preceded by roaring sound. 
O0s emer <2 to ere H. Himtne. cee Rumbling sound. 
Stockton....-.. GOWseres Some persons out | Dull rumbling sound just preceding shock; 
Of doors ene.. some think it emanated from buildings. 
Westley ....... W. G. Carey | Men sleeping on | Heard terrible rumbling 30 s. before shock; 
scow on river.. came out of scow to see what it was, then 
shock came. 
Conejdss. saa H, Picket.se:al)Sames6 occ 2. <2 Awakened by noise like locomotive coming at 
full speed. 
Santa Barbara | J. A. Dodge. | Neighbors....... Rumbling just before shock. 
Lone Pine, Ne- | G. F. Marsh. | Same............ Slight rumbling sound like wind blowing. 
Vadae seme 
Ballarat, Inyo |D. C. Pickett | Same...........-. Awake and up. First indication of earthquake 
Countyzeeeee was low, distant, and increasing roar. 

















VISIBLE UNDULATIONS OF THE GROUND. 


The earth-waves generated at the fault past thru the earth’s crust with a velocity of 
probably from 2 to 3 kilometers per second. The undulations of the surface due to the 
passage of such waves would be so swift that they would scarcely be observed visually. 
Yet there is considerable testimony, of a consistent and independent character, that 
much slower undulations were observed. This testimony comes from various parts 
of the region disturbed, and a great deal of it is positive and unequivocal as to what 
seemed to be the fact. The evidence indicates that there is a type of wave in the ground, 
in the region of high intensity, which has not yet been sufficiently recognized, and the 
origin of which is obscure. Some 20 or more observations bearing upon this class of 
phenomena are here summarily recorded : 

Judging from the descriptions given, these waves behaved like undulations in water, 
with an oscillation approximately normal to the surface. They were for the most part 
observed on alluvial tracts, but some of the reports come from districts where there is 
but a thin veneer of alluvium or soil upon the rocks. If it should prove, on the basis 
of more abundant evidence, that these waves are peculiar to alluviated basins, they 
may be explained as reflections from the rocky slopes of such basins. If a bowl of liquid 
be tapt smartly, vibrations are inaugurated in the rigid bowl which have a speed so 
great that the secondary waves generated in the liquid pass out from all parts of the 
walls of the vessel sensibly at the same instant. But the secondary waves thus gener- 
ated in the liquid have so slow a rate of propagation that they are quite apparent to 
the eye, and in the central part of the surface of the liquid, when the waves meet, there 
is a violent commotion. If, instead of a bowl of liquid, we have a rock basin filled with 
water-saturated alluvium, it seems probable that a similar effect would be produced 
in a modified degree; and the visible waves at the surface may have had such an origin. 
But whatever be their origin, it is apparent that they must be a large factor in damaging 
structures situated upon the ground in which they occur, and so raising the apparent 
intensity on any scale based on destructive effects. 

Freshwater, Humboldt County (S. i. Shinn). — My orchard raised up between 2 and 
3 feet like a big breaker coming in. 

Ferndale, Humboldt County (A. W. Blackburn). — Those who claim to have been out 
of doors when the shock came, state that the earth rose and fell like the waves of the sea. 

Fort Bragg, Mendocino County (O. F. Barth). — A man walking along the street was 
thrown down. He is positive the wave traveled southwest. The ground undulations 
were 2 and 3 feet high. 

Point Arena, Mendocino County (W. W. Fairbanks). —'The ground moved in undu- 
lating swells or waves, rising and falling. 


VISIBLE UNDULATIONS OF THE GROUND. 381 


Santa Rosa, Sonoma County (Miss Locke). — A man saw an earth-wave 2 feet high. 

Cotati, Sonoma County (C. 1. Jeffrey). — The surface of the earth waved like water. 

Napa, Napa County (T. Hull). — Those who were out of doors say the trees bent as 
the shock came like a wave of the ocean. 

Pleasanton, Alameda County (Miss F. Locke). — A lady near Pleasanton saw the earth 
go in waves like the ocean. 

San Francisco (Miss F. Locke). — A fireman at the engine house 1757 Waller Street 
said the ground went in waves. 

San Mateo, San Mateo County (Mr. Maxwell). — The earth rose and fell like the swell 
of the sea, the swells being about 3 feet high. 

Saratoga, Santa Clara County (Louise M. Atkinson). — Distinct waves past over the 
ground from northwest to southeast, the orchard trees rising and falling on each wave, 
like ships at sea, while the electric poles along the road leaned this way and that, some 
seeming almost to touch the ground. 

Santa Clara, Santa Clara County (I. H. Snyder). — Mr. Dan Pickering, living a mile 
south of Santa Clara, says that the ground rose and fell in waves about a foot high. 
Others say that the orchards seemed to be agitated by a wave-like motion. 

San Jose, Santa Clara County (W. S. Prosser). — Many persons saw waves in the 
ground. Sifting out exaggerations, these appeared to be rather more than a foot in 
height. The best observer estimated the distance from crest to crest at 60 feet ; others 
much less, but they must have been greater, for there is no evidence which shows any 
such vertical cracks as would have been produced by short waves. <A good observer 6 
miles southwest of San Jose described the waves as parallel with certain tree rows which 
are northeast and southwest; and the waves moved from him at right angles to the line 
toward San Francisco. Another person, 6 miles northwest from San Jose and looking 
south, saw the waves (which he thinks were east and west) coming toward him, and 
hence toward San Francisco; but about the middle of the quake these were met by 
other waves and the whole surface resembled hillocks or cross seas, and the tree-tops 
waved wildly. To the man to the southwest of San J ose, however, the tops of the trees 
were almost still, while the trunks waved sinuously. 

Meridian, Santa Clara County (G. A. Waring). — A lady reports seeing waves travel- 
ing southward along the driveway, and a man reports seeing a heavy wagon move back 
and forth several times, 4 or 5 fect along the driveway. 

Campbell, Santa Clara County (F. M. Righter). — People out of doors at the time state 
that there was a very rapid wave-like motion of the surface of the earth. 

Wright, Santa Clara County (Flora E. Beecher). — Mr. Deacon, our neighbor, rose 
and stood by the window, and he declares that the ground rose in waves. 

Coyote, Santa Clara County (G. A. Waring). — Near Coyote a man reports having 
seen a northwest-southeast fence move in a wave-like motion, beginning at southern end. 

Paicenes, San Benito County (G. A. Waring). — Toward the Cienega Lime Kilns, 4 
miles south of Paicenes, a man reports seeing a wave coming westward thru a grain field. 

San Lucas, Monterey County (G. A. Waring). — West of San Lucas the waves were 
reported to have been seen moving southward over the hills. 

San Luis Ranch, near Pacheco Pass (G. F. Zoffman). — Mr. Mills stated that the sur- 
face of the ground moved up and down like the waves of the ocean. 

Mendota, Fresno County (G. F. Zoffman).— The people who observed the plains at 
Mendota said that they assumed a wave-like appearance, and that the trains rose and 
fell as the undulations past beneath the tracks. They also stated that this wave-like 
appearance was confined to the north and south movement, the east and west motion 
being more in the nature of a tremor. 

Visalia, Tulane County (F. A. Swanger).— The movement of swell and fall of wave 
seemed strong. 


PATHOGENIC EFFECTS OF THE EARTHQUAKE, 


A curious and fortunately trivial effect of the earthquake was the production of nausea. 
This was observed especially in the region of slower motion of the earth, beyond the 
zone of destructive effects, but one or two cases being reported from the region of 
high intensity. The sickness produced was in most cases apparently similar to sea- 
sickness, and ascribable to the swaying of the ground. In the few cases which occurred 
in the region of quick motion, the nausea was more probably due to nervous shock. 
Brief mention is here made of the cases reported, tho there were probably many others. 

At Ruby, in Siskiyou County (R. E. Madden), intensity III-II, persons were slightly 
nauseated or rendered dizzy, but the feeling past instantly. At Upton, Siskiyou County 
(EK. R. Dixon), intensity IV-III, people felt seasick. Mr. J. H. Roberts, of Yuba City, 
intensity VI-V, reports that 5 persons on his place were made quite sick. In Marys- 
ville (R. F. Watson) the shock caused a dizzy feeling. At Stockton (. Hughes), in- 
tensity VI, a considerable number of people suffered from nausea and dizziness, with 
headache, for a time after the shock. With some these disagreeable symptoms per- 
sisted all the following day. At Modesto (KH. Hughes), intensity VI, a number of 
people were affected by symptoms somewhat like those of seasickness for several hours 
after the shock. San Francisco (Miss F. Locke). Mrs. E. was nauseated by the earth- 
quake and felt pains in her heart. Several people were nauseated by the motion of 
the ground at Pescadero, San Mateo County, intensity VIII-VII. (G. A. Waring.) 

In Bear Valley, San Benito County (G. A. Waring), intensity VI-V, a man out-of- 
doors became dizzy and nauseated, but did not at the time realize the cause. Thru 
the south end of the valley several people became dizzy. Between Mendota and Coa- 
linga (G. F. Zoffman), intensity VII-VI, many persons suffered from a nauseating sen- 
sation. At Conejo, Fresno County (E. Pickett), intensity VI, the earthquake made 
some people sick at the stomach. At Santa Barbara (J. A. Dodge), intensity III, a 
woman who was out-of-doors at the time of the shock was made slightly dizzy. In 
Gardnerville, Nevada (J. A. Reid), intensity IV, a number of people complained of 
a feeling of nausea while eating breakfast at the time of the earthquake, but they felt 
no motion. At Yerington, Nevada (G. D. Louderback), intensity IV—III, one person 
experienced a dizzy sensation. At Lone Pine, Nevada (M. 8. Dearborn), intensity IV, 
a good many people when they first felt the shock thought that they were simply dizzy. 


EFFECT OF THE EARTHQUAKE ON ANIMALS. 


Miss Finette Locke, of Santa Cruz, has interested herself in an inquiry into the be- 
havior of animals at the time of the earthquake, and has prepared lengthy notes reciting 
incidents which were reported to her as the effect of the main shock and the after- 
shocks upon animals in various parts of the Coast Ranges extending from Santa Rosa 
to Santa Cruz. Her notes, which refer chiefly to domesticated animals, form the basis 
for the following summary statement: 

Horses. — Horses whinnied or snorted before the shock and stampeded when the latter 
was felt, some falling owing to the commotion of the ground. Horses in harness became 
frightened and ran away, while others stopt and screamed. Some horses with riders 
in the saddle stumbled and fell; others stood and shivered. A mule near Santa Rosa 
refused to eat all day. A farmer in the same neighborhood observed his horses moving 
about, whinnying and snorting, and called to his boy, who was with them, inquiring 
what was the matter, but before the boy could answer he felt the shock. In a stable 


of 30 horses on Alabama Street, San Francisco, all reared, snorted and jumped before 
382 


EFFECT OF THE EARTHQUAKE ON ANIMALS, 383 


the stable-man, who had just fed them, knew the cause of the trouble. Of the 30, all 
but 5 broke their halters and came toward the stable-man, who had to keep them off 
with a pitchfork. Several horses at the various engine houses of the San Francisco 
Fire Department became frightened and broke away from their stalls. In stables 
generally horses broke away from their stalls, and some failing to break loose lay down. 

Cattle. — Cattle on the hills came down to lower levels, and in some localities did not 
return to the hills for some days after the shock. Cows in corrals near the fault-line were 
in many localities thrown to the ground; others stampeded and ran about wildly. At 
Olema cows in the milking corral were thrown to the ground and rolled over, and as 
soon as they could stand they stampeded. The stampeding of cows from the milking 
corral was reported at many ranches. Several instances were reported where cows 
stampeded before the shock was felt by the observer. In other cases cows about to be 
milked are said to have been restless before the shock and to have lain down as soon as 
the shock was felt, some giving less milk than usual. Two cows near Duncan’s Mills 
are said to have died as a result of the shock. Several cows dropt calves prematurely. 
Lowing and bellowing of the cattle at the time of the shock was very commonly reported, 
and in some cases this is said to have occurred a little before the shock. 

Cats. — Various reports regarding the behavior of cats at the time of the earthquake 
and the after-shocks indicate that they became alarmed. Some rushed about wildly, 
with big tails and bristling backs; some hid in dark corners and otherwise behaved 
abnormally; some disappeared for several days after the shock. In the after-shocks, 
cats seemed to perceive the tremor before people did, and crouched in fright or ran. 
At Olema 7 cats were not seen for 2 days after the shock, and in Alameda some cats 
disappeared for 3 days. Some carried off their kittens. 

Dogs. — Dogs generally became alert before the after-shocks, and barked, whined, 
or ran to cover. After the shock some ran away and did not return for a day or several 
days. Some barked at the time of the shock and ran about with their tails between 
their legs. Many sought the protection of houses and stayed close to people after the 
shock. One dog near Santa Rosa ran about the house for 10 seconds before the shock 
was felt, and then jumped out of an open window down one story to the ground. Some 
dogs were in an excited condition, running about vaguely for some time after the shock; 
and this was repeated at the after-shocks. Others ran straight away at full speed. 
Some bitches brought their puppies to what apparently seemed to them safer quarters. 
Some took to their beds for several days after the shock and others refused to eat. The 
most common report regarding the behavior of dogs was their howling during the night 
preceding the earthquake. 

Chickens.—Chickens generally ran for shelter to their houses, with their wings out- 
stretched, squawking. 

Wild animals in confinement. — The wild animals in confinement at the Chutes, San 
Francisco, crouched and remained quiet. during the shock, but roared after it was over, 
led by the elephant. The elephant also roared at the times of the after-shocks. 


MINOR GEOLOGICAL EFFECTS OF THE EARTHQUAKE, 





LANDSLIDES. 


There are three types of landslides known in the Coast Ranges. For convenience 
in reference they may be designated as earth-avalanches, earth-slumps, and earth- 
flows. The first and last of these are of somewhat. exceptional occurrence, but the 
second is exceedingly common. These landslides are of geological importance as an 
agency concerned in the evolution of the geomorphy of the Coast Ranges of California 
to an extent equaled in few other regions; and it becomes a matter of interest to appre- 
ciate the rdle played by earthquakes in promoting the efficiency of this agency. The 
activity of all three kinds of landslides is related directly or indirectly to the earthquake 
of April 18, 1906. In order to appreciate certain phases of the relationship, it will be 
of advantage to state briefly, in a general way, some of the characteristics of these dif- 
ferent types of landslides. In doing this, reference will first be made to the most com- 
monly occurring type, the earth-slump. The other two may then be characterized by 
contrast with this type. 

Under normal conditions, earth-slumps appear chiefly as features of mature slopes 
which are in adjustment to the ordinary processes of rain erosion. They are also found, 
however, as notable features of immature slopes, at the base of which horizontal cor- 
rasion is active, as on sea-cliffs and stream-cliffs, supplanting under certain conditions 
the earth-avalanche which is chiefly found in such situations. On the mature slopes of 
the Coast Ranges of California, under present climatic conditions, the regolith or mantle 
of decomposed rock, on the more common rocks, appears to be accumulating at a some- 
what faster rate than the rain-wash can remove it. This excessive accumulation of the 
regolith appears to be an important factor in producing conditions conducive to earth- 
slumps. The climate of the region is characterized by a pronounced alternation of 
dry and wet seasons. In the summer the soil and regolith on the hillsides are dried out 
to a considerable depth, in many cases down to the underlying firm rock; and as the 
desiccation proceeds the soil shrinks and cracks. The cracks thus formed permit the 
ready access of the early winter rains to the deeper portions of the soil and regolith. The 
concentration of the entire rainfall in one half of the year is also more conducive to the 
saturation of the ground than if it were distributed thruout the year. The climate 
is thus a contributory factor to the prevalence of earth-slumps. 

A factor of local importance is the character of the underlying geological formations. 
Where these consist of clays or shales, earth-slumps are much more liable to be inau- 
gurated and to recur than where the rocks have little or no clay in them. The emergence 
of springs on hillsides is also a fruitful cause of earth-slumping where other conditions, 
particularly the last mentioned, are favorable. Another factor may be the recent sub- 
jection of the hill-slopes to grazing and tillage. In general, however, this interference 
with natural conditions appears to have been conducive to excessive corrasion and 
sapping, rather than to slumping. Grazing and tillage rob the surface of its natural 
protection of dead grass and other vegetation, which in the early winter season tend to 
restrain the rapid flow of the rain-water and its concentration in lines of corrasive activity. 
New lines of corrasion are thus inaugurated, and where the rocks are but slightly coherent 

384 


MINOR GEOLOGICAL EFFECTS OF THE EARTHQUAKE. 385 


new geomorphic forms, of the bad-land type, are evolved with startling rapidity. This 
colrasive process is sometimes complicated by earth-slumping. 

The activity of earth-slumping as a degradational process is, in general, a function of 
the amount of rainfall in any given season. Thus in the winter of 1889-1890, in which 
the rainfall was exceptionally heavy, earth-slumps thruout the Coast Ranges were 
much more active than in seasons of normal rainfall, and many new ones were started. 
In all such earth-slumps the saturation with water of the soil and regolith, and in some 
cases of the underlying formations, is an essential condition. This water is the main 
agent in loosening or disintegrating the material preparatory to the slip. It is also a 
motive power on account of the large addition which it makes to the weight of the un- 
stable mass; and it is a transporting agent owing to the fluid or plastic nature which it 
imparts to it. 

The character of the movement in an earth-slump is noteworthy. The ground moved 
drops away from the slope in the form of a bite, leaving a lunate or horseshoe-shaped 
scarp overlooking the sunken area. As the mass moves down, it generally encounters 
the resistance of more stable portions of the slope below, and is thus crowded upon 
itself. ‘The plastic mass is in this way deformed, and the deformation amounts in many 
cases to an effective rotation of the moved portion upon a horizontal axis. The lower 
portion is thrust over the passive ground at its lower margin, and the slope of the sur- 
face of the moved part is greatly diminished and in many cases reversed. Between the 
reversed slope and the limiting scarp a depression is thus formed which may become 
a pool. The change in the slope thus occasioned gives rise to the landslide terrace.! 
This kind of movement may be slowly continuous for considerable periods, or it may be 
fitful, depending upon the supply of water. In a slumping tract the movement may 
be repeated at various levels, giving the slope an irregularly stept or terraced profile; 
and if the movement has been recent, numerous cracks and fissures traverse these terraces, 
particularly where they break away from the upper limiting scarp. 

The instability of the mass is an essential feature of the earth-slump. When not 
actually moving, its movement is imminent at all times, but with varying degrees of 
imminence, depending upon local conditions. This instability and imminence of move- 
ment is true of many slopes where no actual earth-slump has appeared, but where move- 
ment may be inaugurated at any time by an exceptionally heavy winter or by some 
other precipitating cause. Severe earthquakes constitute one of these precipitatory 
causes. ‘Thruout the Coast Ranges of California the small residual stability of many 
earth-slumps was overcome by the vibration of the ground at the time of the earthquake 
of April 18, and they were caused to slump forward. In many other instances new 
earth-slumps were started, owing to the same general cause. Besides the earth-slump 
movements which were the immediate effect of the earthquake shock, there were doubt- 
less others which were indirectly referable to the same cause. As will be shown in an- 
other part of this report, one effect of the earthquake was the derangement of the normal 
movement and amount of flow of underground waters, the general result being a tem- 
porary increase of flow. Inasmuch as many earth-slumps depend for their water upon 
springs, there can be little doubt that the increased flow had its effect upon these, and 
promoted their activity several days or possibly weeks after the shock itself. 

Another way in which the shock conduced to the activity of earth-slumps at a later 
date than the shock itself was by opening cracks and thus rendering the deeper portions 
of the unstable mass more accessible to the rains of the following winter. The move- 
ment of earth-slumps at the time of the earthquake was abnormally large and sudden, 
thus leading to the development of numerous open cracks, not only in the landslide 
proper, but also in the surrounding slopes above the limiting scarp. The effect of this 


1See U.S. G. S. Monograph, I, Lake Bonneville, by G. K. Gilbert, p. 83. 





2c 


386 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


would inevitably be the enlargement of the area of the slide in the wet season. Sim- 
ilarly on many slopes, particularly at points not far distant from the Rift, numerous 
cracks were opened without actual slumping of the ground occurring in consequence of 
the shock; but the conditions were thus provided for the slumping process the following 
winter. During the winter 1906-1907 many such slides were reported in a general way. 
Unfortunately detailed information as to their occurrence is as yet lacking. It is to be 
noted that an exceptionally heavy rainfall conspired with the conditions established 
by the earthquake to produce these. landslides. 

In the type of landslide thus far considered, the contained water, which is at once in 
part the cause and the means of the movement, accumulates relatively slowly, and it 
varies with the season, there being usually a more or less free drainage from the lower 
portion of such slides. There are, however, other landslides which are due to a relatively 
large and sudden accession of water to the unconsolidated materials of a slope. Such 
sudden accessions of water may be conceived to be produced in a variety of ways; such, 
for example, as a so-called “cloudburst” in a desert canyon, the slopes of which may 
be heavily mantled by earth and loose rock; or the breaking of a barrier which retains 
a bog or other body of water. For the present purpose, however, which is not that of an 
exhaustive systematic discussion of this class of phenomena, it will be sufficient to take 
note only of water which is expelled from the ground by the compressive action of the 
earthquake shock. Such landslides may be discriminated from earth-slumps by reason 
of their greater mobility, under the designation earth-flow. Earth-flows differ from 
sarth-slumps not only in the much larger quantity of water involved in their mechanism 
as a moving mass, in the suddenness with which the water becomes efficient as a trans- 
porting agency, and in the rapidity of the movement; but also in the brevity of the 
entire process, its finality, and its non-recurrence. 

Besides these two types of landslides, there is still another, which is immediately asso- 
ciated with earthquakes as a cauise of movement. ‘This is the slide of dry earth and 
rock upon precipitous slopes or their fall from cliffs. Soil or other loose forms of earth 
may participate in such landslides, but the material is usually composed chiefly of rock 
which becomes increasingly shattered with the progress of the slide. Such landslides 
will here be referred to as earth-avalanches. They are distinguished from both earth- 
slumps and earth-flows by the character of the material and by the absence of water 
as gn essential factor in producing movement. They also differ usually in the marked 
acclivity of the slopes on which they occur. They differ from earth-slumps, but resemble 
earth-flows, in the finality or completeness of the movement. They are not progressive 
movements, but sudden events; and there is no recurrence of movement of the material 
involved, altho the avalanche may recur at the same place. 

Besides these three types of landslide, another ought perhaps to be recognized. This 
is the form of superficial earth movement which occurred in consequence of the earth- 
quake shock on the alluvial bottom-lands of many streams. It may appropriately be 
designated an earth-lurch. It varies from the opening of a mere crack, with a slight 
movement of the ground on one or both sides, to a violent and complicated deformation 
of the surface, usually accompanied by cracks and open fissures parallel to the trend 
of the neighboring stream trench. These cracks and fissures cut the ground up into 
strips or prisms which lurch toward the stream trench, or, it may be, toward an aban- 
doned slough, the lurch usually being accompanied by a rotation of the prism. They 
are distinguished from all other forms of landslides by occurring on perfectly flat. ground 
and by the fact that they are apparently referable directly and solely to the horizontal 
jerk of the earth movement during the earthquake shock. 

A brief account, which in some cases amounts only to a mention, will now be given 
of some of the various kinds of landslides set in motion by the earthquake. 


MINOR GEOLOGICAL EFFECTS OF THE EARTHQUAKE. 387 


EARTH-AVALANCHES. 


Warth-avalanches were caused chiefly along the sea-cliffs of the coast on the morning 
of the earthquake, tho some also occurred on steep canyons within the zone of high inten- 
sity. On the coast the earth-avalanches were for the most part simply an exceptional 
incident in the normal process of cliff recession. Where the upland of the Coast Ranges 
approaches the shore, the horizontal corrasion of the waves maintains a steep sea- “cliff; 
and the recession of the sea-cliff is effected by the repeated occurrence of earth- avalanches 
due to the undermining by the sea, combined with the disintegrating action of atmos- 
pheric agencies. Pers are thus always upon the face of the cliff masses of earth or 
rock, the fall of which is imminent and may easily be precipitated by a severe shock of 
earthquake. 

The most notable of the earth-avalanches occurred where the sea-cliffs are highest and 
steepest. This happens on the coast of Humboldt County, between Cape Mendocino 
and Point Delgada. Not only are the cliffs here particularly favorable for large earth- 
avalanches, but the coast here is close to the line of the fault which caused the earth- 
quake, and so received an exceptionally severe shaking. For many miles of coast there 
was a general slipping of rock and earth into the sea, down very precipitous sea-cliffs 
ranging up to over 2,000 feet in height. Between Shelter Cove and Point Arena, the 
sea-cliffs are not so high nor so continuous, but there was nevertheless a very general, 
and locally large, shedding of material from their face; and the sea was muddy for many 
days after the earthquake in consequence of the dejection of the débris upon the shore, 
within range of the attack of the waves. 

From Point Arena southward to Fort Ross, the cliffs are low, being for the most part 
not in excess of 100 feet. Harth-avalanches were nevertheless of common occurrence 
along this stretch of coast. South of Fort Ross to Bodega Head the cliffs are again, 
as far as the mouth of the Russian River, several hundred feet high and very steep. 
Here again earth-avalanches were extensive. The rocks along this entire stretch of 
coast from Cape Mendocino to Bodega Head are prevailingly sandstones and shales. 
On the sea-cliffs on the north side of Bolinas Bay and west of the town of Bolinas, there 
was a very general crumbling and fall of the sea-cliff upon the beach. South of the 
Golden Gate, the most notable earth-avalanches were along the sea-cliffs between the 
eity and Mussel Rock. This cliff has a length of about 6 miles and ranges in height 
from about 100 feet up to 700 feet, and is cut almost wholly in the strata Bf the Merced 
(Pliocene) series, which are inclined at angles varying from 15° to 75°. The rocks are 
for the most part rather soft and (esherent, tho there are numerous well-cemented 
and indurated beds in the series. This cliff converges on the fault at a small angle, and 
intersects it at its south end near Mussel Rock. The cliff was severely shaken and great 
quantities of earth and rock were caused to fall or slip down. The great. earth-slump 
at Mussel Rock (Plate 129c, D) was also notably accelerated. A similar sudden 
movement of the ground occurred on the west side of Merced Lake, whereby a large sec- 
tion of the slope sank toward and into the lake, and a portion of the bottom of the lake 
was lifted above the surface by the deformational rotation of the collapsed ground. 

To the south of Mussel Rock there were several small earth-avalanches along the 
cliffs, and numerous cracks were formed near the brink of the cliffs which will in future 
doubtless lead to further falls from the cliff-face. Near San Pedro Point there was a 
large movement of the earth on the face of the high cliff. One earth-avalanche to the 
north of the Devil’s Slide started about 800 feet above the shore and swept the face of 
the cliff, carrying away several hundred feet of roadbed. The slide occurred near the 
contact of sandstones reposing on granite, and both kinds of rock were involved. Smaller 
earth-avalanches occurred farther south on the sea-cliffs. 


388 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


Inland from the coast there were numerous earth-avalanches caused by the earth- 
quake on the walls of steep canyons. One of the most noteworthy of these was on the 
north side of a short but deep canyon west of Chittenden and close to the line of the 
fault.. (Plate 1264.) The rocks composing the side of the canyon are the bituminous 
shales of the Monterey series. The slope rises very steeply for about 500 feet and was 
quite dry before the earthquake, altho it was covered with spring vegetation. Areas 
of bare rock appeared thru this vegetation. At the time of the shock several earth- 
avalanches were started, and these slid suddenly down the slope, part of the material 
filling the bottom of the canyon and part remaining on the less steep lower portions of 
the slope. The larger masses were broken off up near the brink of the canyon. There 
was apparently little or no rotation of the sliding mass. The result was to gorge com- 
pletely the lower part of the canyon with rock débris, to widen the upper part of the 
canyon, and to expose extensive surfaces of unweathered rock. 

On Deer Creek, in the Santa Cruz Mountains, an extensive earth-avalanche started 
near Grizzly Rock and moved westward down a steep, narrow canyon for about 0.25 
mile. (Plates 124p and 125a.) It then changed its course thru an angle of about 60° 
as it entered a wider canyon of lower grade, and following this for another 0.25 mile, 
finally stopt at the Hoffmann Shingle Mill, which was wrecked. <A fine growth of red- 
wood, some 200 feet in height, was mowed down, and covered to the extent of 10 acres 
or more with from 30 to 60 feet of débris. The trees were from 3 to 10 feet in diameter. 
The main canyon was filled with earth and rock for an average width of 80 yards and 
a length of 400 yards. -'The entire area of the slide‘was about 25 acres. The difference 
in altitude between the point where the slide started and the shingle mill, where it stopt, 
is 500 feet. According to Mr. G. A. Waring, the slide material has a depth of 300 feet 
and is composed of soil, clay, and shale. Mr. E. P. Carey, who examined and photo- 
graphed this interesting earth-avalanche, states that it originated in rock that broke 
away in pieces from the steeply inclined slope at the head of the gulch, leaving a large 
theater-like space, the bare, light-colored rock walls of which were in sharp contrast 
with the surrounding green vegetation. The movement was faster in the center or 
deepest part of the gorge than on the margins. The rock was in general piled up higher 
along both sides than in the center, and many pieces became entangled in the standing 
or uprooted trees. A steep-walled tributary to the southeast of the main gulch supplied 
rock material to the main avalanche, and the 2 streams joined much as confluent glaciers 
do. The material involved in the avalanche showed every gradation from powder to 
angular pieces 30 feet or more in diameter. The surface was uneven thruout. Near 
the mill a man was killed by a tree that fell as the avalanche was advancing. 

Mr. Carey also reports another earth-avalanche located on the Petty ranch, about 
4 miles southeast of the one just described. Here a huge rock mass, which embraces an 
area of about 12 acres at the headwaters of Cauley Gulch, broke away from a ledge and 
dropt, leaving a vertical scarp of 40 feet or more. The rock mass in this case was not 
shattered. It practically maintained its integrity. The narrow gulch below was un- 
favorable for free downward movement. As the block readjusted itself, its upper surface 
became nearly level, but was lower at the foot of the scarp than at its outer edge, thus 
indicating that it had suffered rotation. 

At a point about 1.25 miles west of the Mindego sink, on the ranch of Andrew Stengel, 
an earth-avalanche is reported by Mr. Albert C. Herre. It is on a small tributary of 
Alpine Creek, and about 4 miles southwest of the San Andreas fault at the point where 
the latter crosses Black Mountain into the head of Stevens Creek Canyon. The creek 
here is in a narrow, steep-walled canyon in the bituminous shale of the Monterey series. 
The soil on the canyon side was very shallow, and at the time of the earthquake it was 
shaken down into the bottom of the canyon, leaving the walls absolutely bare in places 


PLATE 124 


A. Maacama earth-avalanche. Tuffs dipping in the direction of the slide, 


C 


Earth 


crest of the ridge. R.S. H. 


avalanche in granite on road near Half Moon Bay. 





E. D, 





B. Maacama earth-avalanche. Aclose view. R. 8. H. 





D. Deer Creek, Santa Cruz Mountains. Earth-avalanche from Grizzly Peak. B. B, 


Ati ee hs 
ay ll = as | 
Pi 
a h 
ma ef . i as 

q ie +3 el 
cer * 
8 Vr TP = 
ay a 
7 q 
’ 
. F 
‘ '% 
4 
\ 
i} 
ti. 
‘ a 
oe 
4, 
h 4, 
‘ 
. we tis 
Pn, 
j 
' Ma ¥ 
i \ : %, 
ae , / 
od + 
> we. 
' 
4 f 7 ba 
a 7 >. . : “= ’ 
LIER AR 
OF THE 
Emo T FP fons 
UNIVERSULT. UF GELEINGE 
. vis 
i 
i 
’ 
‘ 
x; 
‘ 
: ‘ 
> 
y 
i ats 
; Ay 
aaa on 
TS baka : 
Per ke 
<> *, , 
{ Pa | 
vv 
cs? 





ae 


Pubhs 


ate 
: a7 vat 
wa cn ‘a ' 
Ty ; al 
fea 
© 2 i 
ae “ie a 
i 
* 
" 
‘ 
pba 
; OF TH 
UNIVERSITY GF SLUNOIS . 
4 Pa 
ti , ‘ 
‘ , 
vs 
a 
$ 
44 
‘ 
4 
bese, «7 
1 y a 


e 
i 





o-4 
¢ 


be; 


75 


« 
¥ 


a Ce ee es 


iam 
i . 
7 ' : > of 
" » ae 
a‘ 
; 4 - 
‘ > i i 
a r ii & 1. 
= Jot bad 
7 ae ‘ 


PLATE 125 





A. Deer Creek, Santa Cruz Mountains. Lower end of earth-avalanche shown in Plate 124D. E.C. 





B. Scarp of landslide in southeast quarter of section 15, township 16 south, range 12 east, near Cantua. G. D. L. 


MINOR GEOLOGICAL EFFECTS OF THE- EARTHQUAKE, 389 


for a hundred yards at a stretch. The slide extends for 0.25 mile on both sides of the 
canyon. A similar carth-avalanche was caused by the earthquake on the ranch of 
Judge Welch, not far from Long Bridge and within 2 miles of Saratoga. Mr. Herre 
reports that here the soil on the northwest side of a small creek coming down from the 
Castle Rock Ridge, was shaken down for perhaps 0.5 mile, tho not continuously. In 
places the slid material filled up the creek-bed and totally changed the contour. It 
destroyed the road to the ranches farther up the canyon, and wrecked some bridges. 
Along the upper part of the area affected, a vineyard was destroyed; while farther down 
the canyon a heavy forest growth, consisting mostly of redwood, oak, alder, and laurel 
was obliterated. This slide lies in the path of the San Andreas fault. 

Mr. Herre further reports a large slide on the Mindego Ranch, 20 miles southwest of 
Palo Alto. Here, on the north side of Alpine Creek, a tract of some 50 acres sank at 
the time of the earthquake, with little or no apparent forward movement. The tract 
sloped to the south and west, and formed part of a great, open hill pasture, with trees 
and underbrush about the lower or creek side. The creek-bed itself is filled with a growth 
of Douglas spruces and other trees. The land, which before the earthquake was steeply 
inclined, is now comparatively level, the eastern and northern part having sunk perhaps 
100 feet, while that on the west has sunk but 10 or 15 feet. The surface of the sunken 
tract was greatly seamed and cracked, and part of it was flooded, owing to the springs 
uncovered; but otherwise it was unchanged in appearance. There was no piling up 
of earth, nor sliding of one portion over another. A fence crost the tract, and the posts 
on it sank so that but a few inches protruded above the surface; while some Douglas 
spruces also sank several feet into the earth. A number of cattle were on the land at 
the time of the earthquake, but were uninjured. It was a work of great difficulty to 
remove them, block and tackle being necessary. The creeck-bed was apparently not 
affected, nor were the trees in it disturbed. There was no apparent movement of the 
earth into the canyon, but the whole mass seems simply to have been dropt from a steep 
slope to a nearly uniform level, surrounded by the high, blank, almost perpendicular 
walls of earth and rock from which it had been sundered. 

Many other earth-avalanches of minor importance were caused by the earthquake 
in various parts of the Santa Cruz Mountains. At Hidden Villa, 2 miles northwest of 
Black Mountain, large blocks of rock are reported to have rolled down the slopes. There 
were numerous slides along Stevens Creek, due chiefly to the caving of the creck banks. 
Along the ridge road southwest of Stevens Creek, sandstone blocks, some of them 6 feet in 
diameter, rolled down the hills toward the creek. Near Half Moon Bay considerable 
masses of granite were dislodged on a steep slope. (Plate 124c.) On the road along 
Pilarcitos Creek, an earth-avalanche brought down big blocks of sandstone upon the 
road. (Plate 1268.) At Boulder Creek a large portion of the soil was shaken loose 
from an abrupt hill 150 feet high, and fell to the level of the ereek, carrying trees with 
it. At the north end of Ben Lomond Mountain, a slide carried trees and brush down 
to the creck. Near Olive Springs, 12 miles north of Santa Cruz, an earth-avalanche 
demolished Loma Prieta Mill and killed several men. At many places on the south side 
of Corte Madera Creek, huge masses of rock had been thrown down from the steep bluffs 
into the road, completely blocking it. About a mile from the summit of the ridge, where 
the Alpine road enters the Page Mill road, a slide carried away the entire roadbed for 
a distance of about 300 feet. On Purissima Creek a slide filled the road for a length 
of about 100 feet; another, between 0.25 mile and 0.5 mile long, dammed the creek to 
a depth of 25 or 30 feet. A large slide close to Wright Station partly dammed the stream. 
On the western slope of the ridge just west of Skyland, several earth-avalanches were 
caused by the shock; and great slides of a similar character occurred on both sides of 
Aptos Creek for 0.75 mile. Besides these, there were many smaller earth-avalanches 


? 


390 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


in many parts of the Santa Cruz Mountains which can not be enumerated. There were 
also several such slides on the granite slopes of Montara Mountain, farther north in the 
San Francisco Peninsula. 

In the Coast Ranges to the north of the Bay of San Francisco, earth-avalanches were 
not so common away from the coast as they were in the Santa Cruz Mountains. There 
were, however, two notable ones which deserve mention here. The first of these is the 
Maacama slide, 6 miles east of Healdsburg. (Plate 124, B.) The slide is about 0.125 
mile wide at the top, and 0.5:mile long. The rock is a stratified volcanic tuff, and the 
slip was down the dip of the beds. The avalanche cut its way thru a fir forest and 
dammed Maacama Creek. The other is the earth-avalanche which, on May 1, 1906, 
dammed Cache Creek to a depth of 90 feet at a point 4 miles below the confluence of 
the north and south branches of the creek. The rock which fell is red sandstone. The 
width of the slide is 300 feet and its height is 500 feet. The dam thus formed broke 
one week later. This earth-avalanche can not be so directly referred to the earthquake 
of April 18 as the others heretofore described, but it was probably indirectly caused by 
the shock. 


BHARTH-SLUMPS. 


By far the most common manifestation of landslide phenomena was that here referred 
to as earth-slump. It would be wearisome to attempt to mention all the various earth- 
slumps stimulated by the earthquake, even if information were sufficiently detailed to 
make this possible. Only two of the more important slides which have come under the 
observation of geologists will be noted. 

Cape Fortunas earth-slump (F. E. Matthes).—This landslide, immediately south of Cape 
Fortunas, is by far the most extensive one on the northern coast. (See plate 127a, B.) 
In May, 1906, it projected into the ocean for about 0.25 mile, like a hummocky headland 
of irregular outline; indeed, it formed a new cape on the coast-line, but will doubtless 
rapidly be cut back by the action of the waves. Its length, in the direction of its move- 
ment toward the ocean, is estimated at little short of a mile; its width varies from 0.25 
mile to 0.5 mile. Its total descent, from the summit of the higher scarps at its head to 
the level of the sea, is probably less than 500 feet. Its surface is exceedingly irregular, 
with many large humps and hollows. Over large areas the sod is more or less rhythmi- 
cally, broken by deep cracks extending at right angles to the direction of movement. 
These cracks are only a few feet apart, and the sod-blocks between them lie mostly in 
tilted attitudes, making the area exceedingly difficult to traverse. The general aspect 
is not unlike that of a much crevassed glacier. In some places, however, the mass seems 
to have been torn apart so completely that the sod is not merely broken but almost 
swallowed up or buried, the browns and yellows of the under soil being the prevailing 
tints. Around its head are a number of steep scarps, from 100 to 200 feet high. They 
are especially prominent on the north side, and again toward the southeast; but over 
considerable stretches between these two sets, the broken surface of the slide joins the 
unbroken hillsides to the east without significant offset. Owing to this, the slide is 
easily approached from the wagon road (from Centerville to Cape Town), which passes 
close by its head. The longitudinal profile of the landslide is one of gentle slopes for 
the most part; its declivity is not at all great, and in a few places even reversed slopes 
occur. Its noteworthy feature is not its vertical drop but its great forward movement. 
In a sense it has flowed like a partially plastic mass, expanding and advancing 0.25 mile 
‘beyond the coast-line, but descending only a few hundred feet. 

In its general aspect, as well as in the nature of its movement, the Cape Fortunas 
landslide is altogether different from those observed farther south, particularly along 
the mountainous coast both north and south of Point Delgada, which, in effect, did little 





A, Earth-avalanches on side of canyon near Chittenden. A.C. L. 





B. Earth-avalanche in sandstone near Half Moon Bay, Slip on bedding planes. E, D, 


: \ 
rh 
asivy OF WLINOIS 











A. Earth-slump at Cape Fortunas, Humboldt County. A. 8, E. 





B, Earth-slump at Cape Fortunas, Humboldt County. A. 8. E, 


Ss af ai a = "* i i. a 
ata eae F ee 
2 a 
. 2 Yn an 





Ng 
5s 
. . 
. 
j 
, 
’s 
4 
' 
; 
1 
r ‘ 
' 
. St 
vi ce WILY 
i 
eqatiy ¥ 
r = 
' sit 
1 
4 . 
. 
{ 
, 
| « 
, 
‘ 
j 
‘ 
é 
i 
r Ny ] 
S 
ss ws ’ - 4 : 
; A 
Pach ascin ede php seach. dif ae nae 1- ipyh ati? i Ming) geo Te eee 
a ’ re 
h 
j 
= Py 
st 
a i 7 _ 


MINOR GEOLOGICAL EFFECTS OF THE EARTHQUAKE, 391 


else than revive a series of old landslide facets. This may not be apparent to an observer 
on the beach, but is quite striking when the coast is viewed in its entirety from a vessel 
off-shore. ‘These facets existed before this earthquake, and had been recognized as such. 
They are conspicuously outlined against the dark timbered slopes behind them, rising 
from 1,000 to 2,000 feet above the shore, and affording an important series of land- 
marks for the mariner. In strong contrast with these bold mountain forms is the region 
in which the Cape Fortunas landslide took place. The land here can scarcely be called 
mountainous; and while it breaks off in cliffs at the coast and is traversed by many 
fairly deep draws, it is essentially a region ef subdued relief. Great declivities are 
notably absent, except in the sea-cliffs, and even these are only a few hundred feet high. 
At the same time, evidences of former landslides may be seen on every hand. They 
are not extensive, as a rule, and are as likely to occur on gentle slopes as on steep ones. 
In a few cases only is a marked downslip noticeable, resulting in the uncovering of 
a steep scarp; in nearly every instance the dislocated mass appears not so much to have 
sheared off and dropt from its former position, as to have expanded or slumped, with 
an accompanying subsidence of its surface. The billowy and irregularly pitted appear- 
ance of these areas, together with the rank vegetation that covers them, afford the prin- 
cipal marks of identification. Both from their characteristic form, suggestive of plastic 
flow, and from their mode of occurrence, it seems reasonable to infer that ground-water 
plays an important réle in their genesis. They are apparently masses which have 
changed their shape in obedience to a lessening of cohesion in their interior, through 
saturation with water. Whether the movement be initiated by an earth-tremor or 
not, it is in every case essentially an adjustment to a more stable position, rendered 
necessary by a change in the physical constitution of the mass. 

It is to this categury of landslides that the one at Cape Fortunas belongs. While 
there are scarps in various places at its upper end, these are really insignificant features 
alongside of the extensive tract of the slide itself. What downslipping occurred on 
these scarps was merely an incident in the entire movement. Both in the large ratio 
between its horizontal advance and its vertical drop, and in its general appearance, the 
Cape Fortunas landslide is closely analogous to the numerous lesser slides referred to; 
and there is good reason for the belief that, like them, it consisted essentially of an 
adjustment of equilibrium in a partially water-saturated mass. It probably had long 
been imminent before the earthquake started it. 

San Pablo earth-slump. — At the time of the earthquake a landslide occurred on Mills’ 
ranch, which is about 4 miles east of San Pablo. The slide is interesting from the fact 
that a previous geological mapping of the region indicated that the point where it 
occurred was on the line of a fault extending in a northerly and southerly direction 
through the Sobrante Hills. The slide was examined by Mr. Hi. 8. Larsen, who describes 
it as follows: 

There are many other landslides in this vicinity, showing that the country is subject to 
such slides. In this particular case, one of the Castro boys informed me that the main 
part of this slide began during the winter rains, and had fallen a foot or more during these 
rains. The balance of the fall occurred the morning of the earthquake. The slide is on 
the east slope of a steep hillside and extends from the top of the hill nearly to the bottom, 
about 400 feet on the slope. The width is about 1,500 feet. At the northeast corner the 
scarp is greatest, reaching perhaps 50 feet. It gradually decreases, and is very slight for 
the southwest 700 feet. On this southwest 700 feet the only evidence of a slide is the crack 
near the top of the hill. The north 800 feet of ground shows every evidence of sliding. 
The dry ground is much cracked, and these cracks extend up and down the hill near the 
scarp and along the hill where the ground has been piled up. In some places there is a 
network of cracks. On the south side of the main slide the ground has piled up about 10 


feet. This extends along nearly all of the south side, and this tendency to pile up to the 
south is shown in other places. Moreover, the north side shows that the ground has pulled 


392 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


away toward the south. The above shows that the movement was not directly down the 
hill, but was more to the south. The formation is sandstones and shales, with considerable 
soft surface soil. 


The same slide was subsequently visited by Mr. F. E. Matthes, and the following 
descriptive note is by him. (See 
figs. 68 and 69.) 


The slip occurred east of a high ridge 
at the southern end of the Sobrante 
Hills. It covers the northeast half of 
an area whose terraced nature is in- 
dicative of a former landslide of much 
larger dimensions. The accompany- 
ing sketches show the general outlines, 
and a cross-section of the slide. It 
will be noticed that the slide does not 
extend all the way down the slope, its 
lower edges being fully 100 feet or 
more above the bottom of the gulch. 
The lower slopes were not materially 
changed, and but little débris fell into 
the stream-bed. 

A steep scarp has been produced 
east of the crest of the ridge. The 
downslip along this scarp does not 
exceed 50 feet, and decreases both to 
north and south. Along the north 
edge there has been a marked move- 
ment down and southward, the scarp 
there averaging 10 feet. Along the 
south side, on the other hand, the loos- 
ened mass had advanced over the old 





Scale in feet (approx.) surface, presenting a bulging and 
2 uf hh: Contour interval 10 feet (approx) : 
PL PP cracked frontal scarp some 6 feet 
Fira. 68.— Map of landslide caused by the earthquake east high. It appears from this that the 
of San Pablo. movement took place, not along the 


: line of greatest declivity, but in a 
direction somewhat more southward, as indicated by the arrow. The 2 hummocks probably 
existed before the slip occurred, but judging by their greatly cracked and rent surfaces, it 
seems likely that their height has been slightly increased. The main crack, which extends 
southward from the upper scarp, contin- 
ues along the hillside in irregular zig-zags 
for some 300 feet south of the slide. 
(See plate 1284, B.) 





Other earth-slumps referred to under 
the section on the Distribution of Inten- 
sity are shown in plates 125B and 129a, 
By.G.D, 






EARTH-FLOWS. my} 
Unchanged slope 





Mount Olivet Cemetery (A. C. Lawson). 
— Perhaps the best illustration of an Rat 
earth-flow caused by a sudden accession Fic. 69.— Section of landslide shown in fig. 68, along 

; * the line 4-d’. 
of water to the incoherent materials of a 
slope, in consequence of the earthquake shock, is that which occurred in the upper part of 
Mount Olivet Cemetery, near Colma, 9 miles south of San Francisco. The locality is at 
the base of the San Bruno scarp, and about 2.75 miles northeast of the San Andreas 





PLATE 128 





A. Earth-slump east of San Pablo. F. BE, M. 





B. Earth-slump east of San Pablo, F. E. M, 


tlt Oe pe ity 


te 
a 


e* 





129 


PLATE 





A. Earth-slump north of Tomales, carrying railway roadbed with it. Track was straight 
before earthquake. R. 8. H. 





C. Earth-slump at Mussel Rock. Old slide suddenly accelerated by earthquake. 0, 





B. Earth-slump 3 miles northeast of Tomales, at Freeman's. R. 8. H. 





D. Scarp of Mussel Rock earth-slump. 0, 


4 ot ia 
, y 
' 
nN + a =i. 
« i 
; 
¥ 
x * 
+ 





pal ye | 
aaa? me rt 


aera en nee wee paren BF oS RE a 
7 y 2 ‘ Vv. 
i rc 
‘ P ; > 
7 ¥ 
> wa we 
“§ = 
3 4 : 
® Z 
cy t+ © 
ar RO® pa 
Soce, : 
i = a 
ml 
‘ i. 7 : 
> a 2 : 
4 Y 7 . 
. ; / 
‘ * a ee 
: we. 
— 
jf c ; 
‘ 
a 5 
i . , 
2 . of 
ALIS 
' 
Py .* 
r 
: . 
* w % 
x 
= ' <i 
‘ 
+ ve. ‘ 
‘ 
i a . 
‘ey 7 
ae 
iy 
+ 7 ee 
, 
' 
. 
2 " 
io 5 
: sal’ 
- a @ i - 
nile . : 
‘i ‘a | 
1 J i , Pr P < 
er ie pate Barty. et. woe ee ee le 
* » 
~ . rg 
. 
4 
La ’ 
" 
> 
‘ 
* J bd 
j 
' a 
a 
, 
- . . 
i i 


PLATE 130 





A. Earth-flow at Mount Olivet Cemetery, Source of flow, looking down. A.C. L. 





Je 
-t 





3 


PLATE 





L 


C 


A 


thwest. 


Looking nor 


at base of San Bruno scarp 


+ Cemetery, 


lve 


Mount 01 


Earth-flow, 


A 





B. Earth-flow in hills east of Half Moon Bay. R, A, 


ra 





rohan temo: ih dnainen ae spel cian ids wipe Ue uni 1 ee Coens wee bbl 


et ete eect renee Silo 


ome ee 





MINOR GEOLOGICAL EFFECTS OF THE EARTHQUAKE. | 393 


fault at Mussel Rock. The steep slope of the scarp is underlain by hard sandstone of the 
Franciscan series, with but a thin vencer of soil, or none at all. At the base of the scarp 
is the gentle slope of Merced Valley, underlain here by Pleistocene and recent sands. 
The sands, partly eolian, lap up on the lower flanks of the scarp, and mantle the trace 
of the auxiliary fault which follows its base. The sands thus vary in thickness from 
a feather edge to an unknown thickness, which it is believed may be as much as a few 
hundred feet at no great distance from the base of the scarp. ‘Traversing the gentle 
slope of the valley-floor are several shallow arroyos, which head in incipient ravines in 
the face of the scarp. At the moment of the earthquake there was a sudden outgush 
of sand and water at a point at the upper end of the cemetery, close to the base of the 
scarp and quite near, if not immediately upon, the line of the buried fault-trace. This 
stream of sand and water, admixed with the loam of the slope, flowed rapidly down the 
course of a shallow arroyo on a grade of about 1:25 with a depth of from 13 feet in its 
upper part to about 3 feet in its lower. The front of the stream stopt abruptly at a point 
just beyond the roadway about half a mile from the origin. The flow was so rapid that 
it carried away many small trees; a wind-mill was wrecked and the heavy concrete 
blocks which served for its foundation were swept down, with other débris. One of 
the pumping stations of the cemetery was demolished by it, and 2 horses were carried 
off their feet, and were extricated afterwards with difficulty. (See plates 1304, B and 
131.) 

According to Mr. M. Jensen, the superintendent of the cemetery, the entire flow had 
been accomplished within 3 minutes from the time of the shock, and he was at its source 
within 20 minutes after it occurred. The height of the flow within a few hundred feet 
of its source was attested by the mud upon the trunks of some eucalyptus trees near its 
margin. This mud extended up to 13 feet above the bottom of the arroyo. ‘This, 
however, doubtless indicates the height of the front of the stream as it past this point. 
As the flow advanced, its surface near its source rapidly dropt; and by the time the 
front had reached the roadway the stream was probably no deeper at its source than 
at its terminus. Indeed, it seems to have been somewhat less, as there was a marked 
tendency for the sand to pile up at the front by reason of the negative acceleration at 
the front due to loss of water. After the moving mass had come to rest and partially 
dried out, it was found that it had left a streak of muddy sand on the bottom of the 
arroyo averaging 100 feet wide and about 3 feet thick. Taking the length of the flow 
as 900 yards, this gives the total volume of the compacted wet sand as 89,100 cubic 
yards. The cavity in the slope caused by the evacuation of this sand and loam was not 
measured, but was estimated to have a width of 150 yards, a length of 300 yards in the 
direction of the flow, and an average depth of 2 yards. On this estimate, its volume 
would be about 90,000 cubic yards, which agrees quite closely with the estimated volume 
of the material ejected. 

The sand, after it had ceased flowing and had been drained and com pacted, undoubtedly 
held in the voids between the grains not less than 25 per cent of its volume of water. 
An additional 15 per cent would probably give it the necessary fluidity for flow down 
a slope of 1:25. But as the flow was swift, there was an excess of water, so that probably 
25 per cent would have to be added to give it the properties manifested in the actual 
flow. The sand, however, in its original position before the time of the earthquake, 
probably did not contain more than 20 per cent of water, since the upper or soil layer 
_ had been somewhat dried out by the air. To the original sand of the slope, therefore, 
there must have been added 30 per cent of its volume of water to cause it to behave as 
it did. This amounts to 27,000 cubic yards. This water came from ground immediately 
below the source of the flow; and it came in a moment, at the time of the earthquake. 
It is only another way of stating the facts to say that it was squeezed out. There was 


394 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


no disturbance of the soil on either side of the cavity, even in its immediate vicinity. 
On the shoulder to the southeast, where the trace of the auxiliary fault passes over 
practically bare rock, no evidence of movement was detected on critical examination. 
The expulsion of the water was a purely local phenomenon. In attempting to explain 
the cause of it, or to ascertain the local subterranean conditions which conspired with 
the earthquake shock to bring about the event, it should be noted first that on the line 
of the fault-trace there are longitudinal depressions, which appear to be in part structural 
and in part due to erosion following the fault. If one of these depressions should locally 
have the character of a sink, without free drainage, then the sand which filled it would 
be saturated with water in consequence of the rains of the previous winter. It is believed 
that the compressive action of the earth-wave passing through such a pocket of satu- 
rated sand, and reflected perhaps more than once from the containing rock walls, would 
be adequate to expel 27,000 cubic yards of water from the deeper portion and add it 
suddenly to the more superficial portion of the formation, thus bringing about the 
earth-flow. It may be stated in this connection, although it has no conclusive bearing 
upon the question involved, that the sands of the valley generally are an abundant 
source of well water, and that there is a surface well within a few hundred feet of the 
source of the earth-flow, lower on the slope. There was very little water in the arroyo 
before the earthquake and a very insignificant stream afterwards, the latter being prob- 
ably referable to the drainage from the ejected sand. 

Vicinity of Half Moon Bay (Robert Anderson). — The earthquake shock caused the 
appearance of an unusual amount of water at the surface in many places. This was 
noticeable in the vicinity of San Bruno, where several short streams running into the 
bay were flooded by an unusual volume of water during the first days following the 
earthquake, in spite of the fact that it was perfectly clear weather. Instances have 
been cited in the present writer’s notes on the results of the earthquake in the San 
Francisco Peninsula, of water with a salty taste or milky color issuing from springs 
after the shock, and of streams being muddy and flowing with increased volume. ‘These 
facts, and the fact that water continued to issue after the earthquake at the points where 
earth-flows occurred, and where it had not been in evidence before, and that earth- 
flows occurred sometimes on convex slopes where the concentration of water under 
normal conditions would be unlikely, seem to be explainable only by the theory that 
uriderground conduits were disturbed and made more open, that new channels of escape 
for the water were formed, and that water was actually squeezed out of the hills in some 
‘ases by compressive movements. This flowage of water to the surface, in increased 
amounts and sometimes at new places, caused the formation of the earth-flows. The 
places where these debacles occurred may or may not have been previously points of 
concentration of seepage water, and the soil already in part saturated. But it is sup- 
posed that the content of water was increased by the shock, possibly in extreme cases 
by the gushing up of a large volume; and that this increment of water, with its dis- 
integrating, weighting, lubricating, and direct forcing power, aiding the attack of the 
shock on the soil, was the main cause of the earth-flows. 

There is little evidence as to when the flows were first set in motion; whether at once 
during the shock, or later after the lapse of some brief period of time that may have 
been necessary for the accumulation of the water in extra large quantities. 

EKarth-flows originated in valleys, in gullies, or on hillsides. Where the weight of the 
earth, combined with the weight of the added water, was sufficient and the substratum 
of the soil was rendered plastic, gravity caused it to creep like a lava-stream, leaving 
a hollow in the place from which it came and a fan or tongue of débris down the slope 
below. Movement was especially apt to ensue where the ground had been previously 
wet, the intensity of the earthquake shock being particularly great at such points and 


PLATES (32 





B, Earth-flow in small valley near Half Moon Bay. R. A. 


> 


bb 
i n 
° hy 


a ee er 





6 tee abn © 


PLATE .t33 





A. Earth-flow shown in Plate 132 B, illustrating floor of cavity from which flow came. R, A, 





B. Earth-flow 4 miles east of Half Moon Bay. R, A, 


a _— 
ts © 
i 
. 
c 
Rd 
ei 
ih il 


ta 


eee 


VI 


' ‘ + — a” J 
«' * Poa 
Spagna See 
a a ‘ 
b -_ 7 a a) 
fe eee 
hs i ee 
. ~ > @ - 
= 
. aati” ‘ » 
z » Oe 
— _ ; 7 
® 
3 7 ¢ 
t ‘ 
7 : 
5 = 
‘ : ute si 
- F La 
4 
7 ; - , 
7 . ‘ ~) f 
ry 
ot 
P 
7 aie 
’ 
. 
i Mas 
a 
GQ 
‘ 
- 
< * 
dS 
i 
~ 
‘Pe 
. 4 
‘ a 7 . 
: Was ‘ 
“re ce). 
oo a 
Sn -ip Tie 
st r a ' 
\ : r 
, ; , i ey ‘ 
“ L . ; 1 
} aP 
be . 
-, ‘ 
, es 
‘ P : ; 
i Se Pent ‘ Lary ® i, 
4 iw ey. ' 
ul } 
: 7 —* . 
: a a ie ee Pelee 
ae Fo ae ‘ Tx. Sayed be 
71) wai . . 7 Zs 
a : ® 
mz: * ae i an”) we 
‘ : -* RAND pas hme n 
ee ry ae een one ee ee ee ee a 
. 7 7 a ae 
i on a 71 
“ : Lis 
3 oh \ hare PTE | yu. oat 
i 
i 





MINOR GEOLOGICAL EFFECTS OF THE EARTHQUAKE. 395 


the tendency of the vibrations being to set the mass in motion. Earth-flows occurred 
in many places in the Coast Ranges, and probably thruout the region in which the 
shock was heavily felt. The writer found many of them, large and small, on the San 
Francisco Peninsula and in the Santa Cruz Mountains, also in the Mount Diablo and 
Mount Hamilton Ranges. 

Following are descriptions of 5 earth-flows that occurred on the morning of the earth- 
quake in the neighborhood of Half Moon Bay, which is on the coast 25 miles south of 
San Francisco : 

One of them was formed in the hills bordering the terrace at Half Moon Bay, immedi- 
ately south of Frenchman Creek, 1.5 miles north of the town, and a mile from the sea, 
at an elevation of 100 feet. It is pictured in plate 1324. At this place the earth caved 
away in a crescent-shaped area on a slope of only 18°, and flowed out in two long arms 
so as to leave a hole 4 feet deep, surrounded by vertical walls of unaffected soil. The 
flow occurred at a fairly high point ona gently undulating incline. The discharged earth 
was divided by a mound, at a point 150 feet below the summit of the arc, and followed 
two courses which were determined by gullies on both sides. Much of the débris over- 
flowed the central mound at the same time, and inundated the barley fields to a depth 
of 2 to 4 feet, for 100 feet farther. On both sides of the central mound the caving away 
continued to the same depth. In the left-hand fork it stopt within a few feet, and the 
flow did not extend very far beyond. In the right-hand fork a cut 100 feet long and 
50 feet wide was made, the earth flowing down from it 250 feet farther over the grain 
field, as shown in plate 1324. Thus the whole length of the slide was 500 feet. The 
width of the main hole was on the average about 100 feet, and the length, as already 
mentioned, 150 feet not including the arms. 

In this hollow in the hillsides many dry blocks of sod carrying growing grain — usually 
in an upright position — were left stranded 4 feet below the surface of the hill by the 
removal of the subsoil. The fence that crost this area was broken and carried away 
and partly buried. Where the caving ceased in the right fork, a ridge of débris was 
piled up across the mouth of the hole, much higher than the stream of loose material 
that flowed farther. Similar ridges were heapt up across the path of the flow, where 
the breaking away of the hill stopt in the other arm and at the upper end of the central 
mound. 

The south or right arm of the flow extended down the hill at an angle gradually 
decreasing from 18° to less than 5°. Large parts of the fence were carried on its sur- 
face for 300 feet. 

Plate 132 gives a detailed view of the lower extremity of the right arm. The stream 
came to an abrupt stop, like a quickly cooled lava flow, and preserved a face 1 to 2 feet 
in height above the grain field. The surface of the flow consisted largely of blocks of 
sod, usually almost upright, which were carried down from the hole without much 
moistening, or transformation into material capable of flowing. The bulk of the flow 
was a moist aggregate of earth fragments possessing something of their previous form 
and grading into mud, which assumed a semi-fluid consistency underneath. The 
bottom of the hole, and the flow itself, remained too muddy to walk on for wecks after 
the earthquake, and the field below the lower end of the large arm was left marshy, 
tho it had not been so before. It is to be noted that several fairly heavy rains followed 
the earthquake after an interval of several days, and before these earth-flows were 
visited; but these were not sufficient to account for the amount of moisture observed. 
The chief effect of the water was in the ground at a depth of 3 or 4 feet below the sur- 
face. It rendered the soil sufficiently fluid to enable it to flow down the gentle slope, 
probably partly oozing from under the surface crust and partly transporting the sod 
with it. Most of the surface was carried down with the main flow, the stranded sur- 


396 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


face blocks that remained in the cavity being accountable for as fragments from the 
broken edges subsequently giving way and being carried only a short distance as the 
upper end of the flow came to rest. In this way, probably, the walls were trimmed, 
for the cut in general was left remarkably clean. 

Another flow of similar character took place 3 miles north-northwest of the town 
of Half Moon Bay, on the creek next west of Frenchman Creek. It is shown in plates 
1328 and 133A. On the morning of the earthquake an acre of the gently sloping allu- 
vial floor of a broad, short valley tributary to the main creek on the east caved and 
flowed out, leaving an excavation 10 feet deep, where before it had been almost level 
and where there had been no stream channel. In this case, the water already gathered 
in this basin-like valley, which here had had no means of prompt escape, was an important 
aid in the formation of the flow, aside from the sudden accession of water that probably 
caused the earthquake. The presence of a large amount of water and the forcible 
movement during the earthquake shock resulted in the loosening and undermining of 
the ground and its transportation as a fluent mass. The angle of slope was about 5°. 
The flow carried out thousands of tons of earth in this manner and spread it over 
about 2 acres of meadow land, to an average depth of 1.15 to 3 feet. 

Plate 1328 gives a view of this earth-flow, showing the pit from which it was derived. 
Covering much of the surface of the flow and the floor of the hole are to be seen blocks 
of sod which have been carried right side up as if the material had moved en masse. 
The amount of water in evidence shows clearly how the earth was softened and enabled 
to move. The picture was taken two weeks after the earthquake. At that time water 
was still seeping up from underground, and out of the lower portions of the broken 
walls, while the ground near the surface of the valley was quite dry. The water had 
formed two definite rivulets thru the débris, at an elevation above the surrounding 
meadow, and was running in continuous streams, fast cutting a channel for itself and 
removing the soft material. Considerable water was dammed back in the hole by a 
4-foot ridge of débris piled across the mouth of the hole, as in the case of the previously 
described earth-flow. This mound of earth, along the line where the stream left the 
caved-in area and flowed over the preexisting slope, was probably piled up at the last 
by the remnants of the flow gliding down and heaping themselves up as a barrier at 
the mouth of the hole. 

“ The cavity, about an acre in extent, has 10-foot walls which gradually decrease in 
height lower down the valley, the bottom of the hole being more nearly level than the 
valley-floor. Plate 1334 shows part of this flow in detail. 

Some of the great blocks of sod around the edges have not been removed, altho the 
material from underneath has gone. Concentric cracks not visible in the pictures 
extend around the edge of the hole and for 50 feet above its upper end, showing that 
the area affected is broader than appears at first sight, and that the work is not yet all 
accomplished. ‘The material of the valley-bottom is a coarse, arkose earth, derived 
from decomposing granite, and containing many rock fragments. 

A flood of earth covers about 2 acres of the meadow. Water was present in this 
earth-flow in greater amount than in any other that was examined. The nature of the 
material may be judged of by the abrupt face of the stream where it stopt. The edge 
makes a steep angle with the meadow and rises to an average height of 2 feet above 
it. Yet the fact that this mass of earth was able to move more than 300 feet after it 
left the lower end of the hole, and spread into an even and thin layer over a wide extent 
of nearly level meadow, shows that it was fairly soft. It was moved on a basal layer 
of semi-fluid mud and sand, with the aid of the weight of the overlying and partly dis- 
integrated earth. 


MINOR GEOLOGICAL EFFECTS OF THE EARTHQUAKE. 397 


The largest of the earth-flows seen occurred in the canyon south of the house of Mr. 
Nunez, 2.5 miles east-northeast of the town of Half Moon Bay, at an elevation of about 
500 feet. It originated in a manner similar to the others, but in a canyon along which 
there is a distinet but ordinarily dry stream channel. <A long, irregular hole from 4 to 
7 feet deep was excavated near the head of the valley, and a great volume of earth 
flowed down its curving course for 0.25 mile, as far as the Nunez house, and there stopt, 
being in part diverted into the main ereek to which the valley is there tributary. Ac- 
cording to the testimony of witnesses, the flow reached the end of the 0.25 mile in 0.5 
hour after the earthquake shock. It was seen gliding slowly down and engulfing the 
orchard just back of the house. According to observers on the Nunez ranch, the earth- 
flow was not accompanied by any water; but two wecks later, when examined by the 
writer, it preserved every evidence of having been muddy. lispecially was this true 
at the bottom, where great masses of mud stili had the consistency of jelly. It is prob- 
able that there was no flowing water on the surface of this or other earth-flows at the 
time of their formation, and that the presence of water in the flow was not evident to the 
casual observer because of the comparative dryness of the material on its upper surface. 

The slope of the canyon down which the moving body of land crawled is about 25° 
near the head and decreases to 15° farther down. The flow filled this to a width of 
100 feet on the average, and to a depth varying from 10 to 20 feet. The inertia of the 
mass is illustrated by the fact that in the early stage of the flow the earth was piled 
20 feet higher on the hill, on the inside of the big curve made by the canyon, not far 
below the pit, than it was when the flow came to rest. The marks at this elevation 
were probably made very soon after the main mass was discharged from the cavity, 
before it had spread very widely. The central portion of this earth-flow is pictured 
in plate 1318, where it appears as a ridge many feet high rising above the tall erass on 
the hillside, on the right of the picture. The pressure of the material at the head of 
the flow, as it started, was so great that the earth bulged up over the sides in places, 
in such a way as to force upward great blocks of sod and turn them on edge or com- 
pletely over, away from the rim of the hole. 

The flow assumed the form of two lateral ridges and a central depression, or channel. 
The ridge on the west or inner side of the curve was considerably the higher. The 
form was due partly to the concavity of the valley; but chiefly, it is thought, to the 
tendency of the more fluid material to follow the deepest: possible path along the gully 
under the center of the flow. Thus the drier material was retarded at the sides. Sub- 
sequent to the first starting of the flow, a stream of semi-fluid mud and sand continued 
to run down the central channel, covering its sides with a coating of mud and leaving 
flowage striations on it. This channel and its markings are exhibited in plate 131s. 
Two weeks after the earthquake, when the photograph was taken, water was running 
in this channel and had cut down into it several feet deeper. Its bottom, however, was 
still from 5 to 10 feet higher than the bottom of the underlying preéxistent water 
course, where water had not flowed before at this time of the year. The man in the 
picture is standing at the bottom of the gully. To the left of him, the hammer and 
note-book mark the top of one of the parts of the lateral ridge which is here divided 
into several hummocks. To the right is the other and higher lateral ridge. The fore- 
ground was formerly covered by a dense thicket of willow trees. These willows have 
been completely buried, except at the sides where some dead branches protrude. A 
fence that crost the canyon was torn away for 100 feet, and not a trace of it could be 
found. The fence shown in the picture is one newly built in its place. 

Two other smaller earth-flows occurred just over the hill westward from the last one 
described. They are shown in plate 1338, the canyon on the left being the one occupied 


398 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


by the Nunez flow. One of these 2 earth-flows, that at the right of the picture, started 
near the top of the ridge in a depression in the slope, formed a hole 75 feet long and 
40 feet wide, and coursed down a narrow runnel having a gradient of 25° to the bottom 
of the hill, a distance of 600 feet. Enough earth issued to fill up the rather deep ditch 
in the gully clear to the bottom of the hill and to bury the grain field on both sides to 
a depth of 1 to 2 feet. In this case, as in the preceding one, there were formed lateral 
ridges higher than the center, so as to leave a groove between. Down this channel 
there flowed softer material, which lined the sides of the lateral ridges with a smooth 
coat of mud and left conspicuous flowage marks. The flow thus raised a ditch for itself 
above the level of the slope. The earth-flow probably assumed this form by leaving 
behind, at the sides, the material least capable of flowing, and by concentrating its 
most liquid parts along the deep central line. 

The other earth-flow was near by, on the convex face of the knoll in the center of 
the picture. <A similar cavity was produced, from which the contents were spread out 
broadly. It is a good example of the starting of a gully, as there was no depression 
before. One branch of this earth-flow came straight down the hill and slightly toward 
the canyon on the left; the other branch came down toward the gully in which the 
first-mentioned of these 2 earth-flows occurred. Thus drainage lines were started 
which ultimately may separate the central hill from the ridge on the right, of which 
it is now a continuation. The left arm of the flow on the hill may develop a channel, 
as explained below, which will cause the drainage from this hill, which is now toward 
the foreground, to pass into the canyon on the left. 

Similar landslides, tho usually of smaller size, occurred thruout the region neighbor- 
ing the fault visited by the writer, and even in districts at a considerable distance from 
the fault. Frequently they were not definitely referable to the earth-flow type, but 
resembled more closely earth-slumps formed without the aid of a suddenly increased 
water supply. It was often difficult, especially in cases where the movement was 
slight, or the slide was in the embryonic stage, to determine whether the earthquake 
at those points had caused a flow of water or not. In the instances so far described, it 
was pretty certain that it had; but in many others the phenomena were explainable 
as being the result of moisture that was already collected before the earthquake. Many 
slips were formed on hillsides and along the embankments of mountain roads, and along 
the cracks formed by the shock in moist and loosened soil. Often these slips were 
arranged one above another, the perpendicular faces due to slipping having the appear- 
ance of step faults. In such cases the weight of the moved mass and the amount of water 
was not sufficient to cause the material to flow. There were examples of such slips 
along the coast hills north of San Pedro Point, near the road halfway between San 
Bruno and San Andreas Lake, near the road from Belmont to Crystal Springs Lake, 
0.5 mile southeast of the San Mateo Alms House, and in many other places on the San 
Francisco Peninsula. In some places bare ridges had their lines of symmetry broken 
into little knolls and irregularities by these slips, a common occurrence in the hills of soft 
sand formations in the northern part of the San Francisco Peninsula. All the slips 
just referred to illustrated the gradation between earth-slumps and earth-flows. !Doubt- 
less in many of them a small amount of water did gather as a result of the earthquake. 

Relation of earth-flows to rainfall (Robert Anderson). — The rainfall previous to the 
earthquake, tho possibly of little importance in connection with the more extreme types 
of earth-flows, in which practically all the work was done by a head of water brought 
from underground by the shock, bears a close relation to the less extreme types, and 
to the geologically very important doubtful types intermediate between the earth- 
flows and earth-slumps. In a dry year the number and size of all of these would prob- 
ably have been much less. Had covering of slopes been unsaturated, areas might not 


MINOR GEOLOGICAL EFFECTS OF THE EARTHQUAKE. 399 


have been so ready to break forth at a sudden accession of water from below; and the 
rainfall not having been great, there might not have existed such a plentiful source of 
underground water to be drawn from. The following review of the rainfall conditions 
may be of value in indicating a relation between the preparedness of the ground and 
the number and importance of flows and slumps. 

During the first three months of 1906 the rainfall was exceptionally heavy thruout 
California, being on an average thruout the whole State more than 9 inches in excess 
of the normal for that period. Up to the beginning of 1906, the amount of rain for 
the season was 4.5 inches below the average; but owing to the great excess during the 
late winter and early spring months the total for the year up to the first of April, the 
month in which the earthquake occurred, was nearly 5 inches above the normal. During 
January, February, and. March the rain was heavy and continuous. Nearly all the 
rain of the season was during these months immediately preceding the earthquake 
month. Practically no rain fell between April 1 and April 18. 

All of the rainfall data available in the monthly reports of the Weather Bureau for 
California, compiled by Professor McAdie, has been used for calculating the amount of 
rain in 8 counties south of San Francisco. These are San Francisco, Alameda, San 
Mateo, Santa Clara, Santa Cruz, Monterey, San Luis Obispo, and Santa Barbara. The 
average rainfall at 46 different places distributed thru these counties was 22.59 inches 
from September, 1905, to April 1, 1906, between 2 and 3 inches above the normal for 
this region. The excess would have been greater but for the lightness of the rainfall 
during the autumn term, which was 3.55 inches, or several inches less than the average 
for former years. During the spring season up to April 1, the precipitation was exces- 
sive. During the three months that preceded the earthquake, 19.04 inches of rain fell, 
or 84.30 per cent of the whole precipitation up to that time. During the first half of 
April, there was practically no rain at all. Thruout this region, as well as thru Cali- 
fornia as a whole, March was a very rainy month; especially heavy downpours coming 
everywhere in the State during the last days of the month. It was the rainiest of the 
months except in parts of Santa Clara and Santa Cruz Counties, where more fell in the 
month of January. 

The majority of the earth-flows and earth-slumps that occurred were near the coast, 
although the amount of rain that fell was not as large there as it was farther back in the 
mountains. The coast region, however, is subject to heavy fogs, which precipitate some 
moisture and help to prevent evaporation of the moisture already present. These fogs 
were probably a factor in causing the earth-flows and earth-slumps near the sea. The 
principal cases described were near Half Moon Bay. The records from Point Montara, 
only a few miles away, showed that the rainfall in this vicinity was heavier than at any 
other point along the coast south of San Francisco. During the spring season up to 
April 1, it amounted to 23 inches, and during the autumn season it amounted to 12 
inches. The table shows that the heaviest rains were in the Santa Cruz Mountains. 
At Boulder Creek, in Santa Cruz County, 55.70 inches of rain fell during January, 
February, and March alone, and 16 inches fell during the four months preceding. 

During the spring of 1906, a large part of the precipitated moisture remained in the 
ground, which was previously dry, and the amount of evaporation was minimized by 
the continuous succession of cloudy and rainy days. The year afforded an example of 
the concentration of an excessive annual rainfall into a short period, with all the con- 
ditions favorable for the absorption and retention of the moisture in the ground. For 
this reason, conditions favored the production of debacles of various kinds in the loose 
material covering slopes. 

The earth-flows that have been discust are more or less similar to the flows occasioned 
by the bursting of peat-bogs. The causes of their origin and their nature appear to be 


400 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


much the same.’ Sir William Conway has given an account of a mud-avalanche,’ 
a swift torrent of mud, water, and great rocks, in the Himalayas, somewhat similar in 
nature to these earth-flows. Streams and torrents of mud somewhat analogous but 
usually of glacial or lacustrine origin have been known to flow in the Alps. Mention of 
these has been made by T. G. Bonney.’ 

Earth-flows are important as giving rise to new drainage lines and modifying old ones. 
They are also powerful transporting agents. The initiation of a new drainage line is 
a matter of importance. Once started, it is a point of vantage for the attacks of agents 
of erosion, which thereupon are able to increase their work at an accelerating rate of 
speed. Only next in importance is the definition and fixing of embryonic depressions 
and gullies. Both these processes are carried out vigorously by these earth-flows, 
besides other processes such as the enlargement of valleys and channels already formed, 
the transportation of material, the destruction of the regularity of contours, and the 
transformation of surface rock. material into a form easily removable otherwise, thus 
in every case supplying better leverage for further destructive action. 

Earth-flows usually originate in minor depressions or in already well-formed gullies or 
valleys, these being the places most subject. to the concentration of water: but in some 
instances they occur on the convex face of a slope, where the removal of soil develops 
a depression for the first time, and a new drainage line is made possible. The soft 
débris that is removed, although piled higher than the surrounding slope, lends itself 
easily to the formation of rivulets by the water that rises and collects in the excavation 
that is left. These small water-courses, once formed, control the line of flowage, and 
result in a sort of superimposed drainage when they have worn through the débris to 
the original slope below. Earth-flows of the above varieties, large and small, with the 
closely related types of ear th-slumps, are thus among the important initial steps in the 
development of drainage lines in the California hills. 


EARTH-LURCHES. 


Of the three kinds of Jandslides thus far referred to, the first two, earth-avalanches 
and earth-slumps, occur quite commonly independent of earthquakes. Of the third 
kind, or earth-flows, the only examples that have been presented are immediately con- 
nected in genesis with the earthquake of April 18, although it is conceded that sudden 
accessions of water to loose earth might arise in other ways and occasion earth-flows. 
As regards the fourth type, the earth-lurch, it is difficult to conceive for it any other 
origin than an earthquake, since it is caused directly by the horizontal jerk of the ground 
and can not be produced in any other way. In the detailed account of the distribution 
of apparent intensity, a brief account of these superficial movements of the ground has 
been given and need not here be repeated. They are best exemplified on the flood 
plain of the Eel River, west and north of Ferndale; the flood plain of the Russian River ; 
the flood plain of Alameda Creek, near Alvarado; the flood plain of Coyote River near 
Milpitas; the flood plain of Pajaro River; and the flood plain of the Salinas River. 
(Plates 136a,B and 137a,8B.) In all these. Tees cracks were formed in the alluvium, 
generally parallel to the stream trench, and the ground between the cracks was caused 
to lurch horizontally toward the stream, usually with a rotation of the moved mass, 
which gave to it the profile of a Basin Range fault-block in miniature, the portion of 
the moved strip farther from the stream collapsing into the vacuity caused by the 
lurching. 





1G. A. J. Cole, Nature, Jan. 14, 1897, vol. 55, pp. 254-256. G. H. Kinahan, Nature, Jan. 21, 1897, 
vol. 55, pp. 268-269. 

2 W. M. Conway, Climbing in the Himalayas. New York, 1894, pp. 118, 129-130, 323-324. 

’'T. G. Bonney, Moraines and Mud Streams in the Alps. Geol. Mag., January, 1902, p. 8. 


PLATE 134 





A. Moss Landing. House, tree, and fence moved 12 feet by lurching of ground toward Salinas River. A.C. L, 





B. Moss Landing. Lurching of ground toward Salinas River carried piles from beneath bridge timbers, causing it to collapse. A. 0. L. 


e 
= 


- 


c 
ioe 

Paul 
> «@ 


: 





~ . ‘i 
: ) ; 
* 
S | 
< ; ‘ 
. nail ‘ < 
= ; 
. : a 
-~— —~ 7 
J oa i 
«J ) 
fy 
z ; 


PLATE: 135 


sa 
oH N ye: Deka 





A. Moss Landing. Lurching of ground toward Salinas River, to left, carried piles from beneath bridge timbers and caused bridge 
to collapse. Displacement 9 feet, A. 0. L. 





B. Moss Landing. Deformation of surface due to lurching of ground toward Salinas River. A.C, L, 


vi? 


YO) WUNUR 


‘ars, 


c ws 


b Vives 


= r 


font 


v 


wi. ae 






PLATE 136 





A. Lurching of ground toward Salinas River and consequent collapse. Near Spreckels. A.C, L 





B. A detail of view shownin A, A.C. L, 


*,* 


+ 


tnd 
3 
* 
. 
. 
heat” 
- 
qe 7 
oS i 
< (SF, 
- h) 
oe” Cte 
Len 
ears | 
aa 7 : 
V6 
a 
> » Mt ¢ 
, iS 
ta fp 7 a) ; 
Ds 8 
ee pe meme, ab 
ee 
4 


q > ~~ 
Rie” Pip bem 





PLAT Eats? 





A. Lurching of ground toward Salinas River, with consequent collapse. Near Spreckels. Per J.C, B, 





B. Destruction of road due to lurching of ground toward Salinas River. Near Spreckels, A.C, L. 


, » “f 
4 
t 
, 
' 
~ 
' 
' 
‘ 
* - 
\ 
. 
. 
' 
. 
i 
p 
a bA 
fi, Ae. 
’ 


rd 


ron Wn a ae one 
oo vie ' > oo 
7 - —_— 
aot ee 
aren tes 
‘ 
cre 
. 
: 
: 
= 
‘ 
; 
4 1 
‘ 


LIGITAL : 
GF THE. 
UNIVESSITY OF Linus 





MINOR GEOLOGICAL EFFECTS OF THE EARTHQUAKE, 401 


Along the beach or sand-spit which separates the Salinas River from the Bay of 
Monterey at Moss Landing, there was a marked lurching of the spit toward the trench 
of the river as illustrated in plates 1344, B and 135a, z. 

Lurching of soft ground was also exemplified on the tidal mud flats of Tomales Bay, 
and on the “made land” of San Francisco; but there being no trench in these cases, 
the movement caused a ridging of the surface with compensating depressions. In the 
case of the made land in San Francisco, and perhaps generally, the deformation of the 
surface due to lurching was complicated by the settling together of the loose material. 


CRACKS AND FISSURES. 


The cracks in the ground which appeared at the time of the earthquake fall into 
different categories. Of these there are two distinct classes: 

1. The crack or fissure of the main fault, which is a superficial expression of the deep 
rupture of the earth’s crust that caused the earthquake. Associated with this as a sub- 
class are the auxiliary cracks and fissures which are superficial expressions of branch 
ruptures or subparallel ruptures, generally close to the main rupture in the Rift zone. 
In this class would also belong any cracks due to supplementary faulting in the general 
zone of disturbance, if such supplementary faulting exists, which is doubtful except in 
special instances. 

2. The second general class includes those cracks and fissures which were caused by 
the earthquake, as a result of the commotion of the ground, and have, therefore, been 
designated as secondary. 

The main crack, or fault-trace, and the auxiliary cracks satellitic to it, have been 
described in the section of the report dealing with the earth movement along the fault. 

The secondary cracks, inasmuch as they are an indication of the intensity of the shock 
at any locality, have been described or referred to in the section dealing with the dis- 
tribution of intensity. A brief review of the phenomena of cracks in the ground, apart 
from the main fault-trace and the auxiliary cracks in the Rift zone, will, however, be 
given, even at the risk of some slight repetition. 

Since some of the cracks to be referred to can not with certainty be placed in one or 
the other of the two fundamental classes above indicated, it will be found convenient 
not to force that classification in all cases. Along the zone of the Rift there were many 
secondary cracks, as well as those classed as auxiliary; but it was not in every case 
possible to discriminate between them. These secondary cracks occurred both on hill 
slopes and in alluvial bottoms. On the hill slopes they were very commonly associated 
with landslides, or marked the inception of landslides; and these have already been 
discust. On the bottom lands of streams or embayments in the Rift zone, cracks in the 
ground were exceedingly common for the entire length of that portion of the Rift along 
which the fault extended. In very many cases these cracks were associated with the 
lurching of soft incoherent materials, just as the cracks on the hillsides were associated 
with more common phases of landsliding. There were also, however, many cracks 
quite dissociated from the deformation of the surface due to lurching, although there 
was doubtless in these cases an ineffective tendency to lurching. 

Beyond the zone of the Rift, cracks were observed at many localities. These were 
most common on the bottom-lands of the streams, notably the Kel River (plate 1384, B), 
the Russian River (plate 139, 8), Coyote Creek (plate 140a, 8), and other streams at 
the south end of the Bay of San Francisco, Pajaro River (plate 1418), San Lorenzo River, 
and the Salinas River. Many other smaller streams might also be mentioned. In 
these cases the cracks were usually associated with the phenomena of lurching of the 
alluvial deposits, though many cracks also occurred where no such association was ap- 
parent. ‘They were in nearly all cases found to be parallel or sub-parallel to the nearest 

2D 


402 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


portion of the stream trench. They very commonly extended for several hundred feet, 
in some instances for several hundred yards, and were characteristically arranged in 
linear series. ‘The cracks in the series in some cases overlapt en échelon, and in others 
they were in groups of parallel cracks in belts a few hundred feet wide. In no case was 
there any suggestion that they were more than purely superficial phenomena. A unique 
manifestation of surface cracks is that described by Matthes and Crandall in the vicinity 
of Livermore. (See plate 141,.) 

On the hillsides and ridge crests, at points not within the Rift zone, cracks were of 
common occurrence. Most of these were connected with landslides, as has been indicated 
in the section dealing with that subject. Roadways and artificial embankments were 
particularly susceptible to damage from such cracks. But some of the cracks had no 
apparent connection with landslides, actual or incipient, and these are of especial 
interest. The most northerly are those described by Mr. E. S. Larsen in the region north- 
west of Covelo, Mendocino County, as set forth in the record of intensity. Some of the 
cracks described by Mr. Larsen crost the crests of rocky ridges; and altho it was not 
possible to follow them for great distances, they evidently extend down into the rock. 
It is remarkable that in the district where these cracks occur, there was no evidence 
of a local rise in intensity and, therefore, nothing to suggest that they were the seat of 
a supplementary local earthquake. The probable interpretation of the occurrence is 
that they are secondary cracks of a rather exceptional kind, in ground that required 
no very severe shaking to rupture it superficially. Cracks of a similar character were 
noted by Mr. C. E. Weaver in the Clear Lake district and on the flanks of Mount 
St. Helena. 

On the San Francisco Peninsula, similar cracks were observed by Mr. R. Crandall on 
Cahill Ridge and Sawyer’s Ridge, and are described by him in his account of the dis- 
tribution of intensity in that region. In the Santa Cruz Mountains, such cracks were 
common and are described more-or less in detail in the section on the distribution of 
intensity. In general they appear to be the result of the earthquake rather than a con- 
tributory cause, although in some cases it is quite possible that they may have been local 
ruptures of the nature of auxiliary cracks and so gave rise to subordinate vibration. 


EFFECT OF THE EARTHQUAKE UPON UNDERGROUND WATERS. 


SIGNIFICANCE OF THE PHENOMENA. 


Perhaps the most interesting and significant fact which the study of the earthquake 
has brought to light, apart from the great fault along the Rift, was the general disturbance 
of underground waters. In earthquakes generally, the phenomena which appear at the 
surface of the earth have become well known and, indeed, almost commonplace in recent 
years; but what transpires in the earth’s crust below the surface, as the earth-waves 
generated at the seat of disturbance pass through it, is as yet a matter of uncertainty 
and inquiry. The effect of the shock upon the movement of underground water, as 
manifested by the behavior of springs and wells, throws light on this question. A few 
pages are, therefore, devoted to recording information of this kind. 

It appears from the reports that have come in that springs and wells were very gener- 
ally and variably affected throughout the disturbed area, indicating a sudden derange- 
ment in the normal movements of such water. This derangement could only have 
been effected by the changes in spaces in the rocks in which the waters in the subsur- 
face region are contained, whether flowing or stagnant. These spaces are of 4 general 
kinds: (1) interstitial spaces, or so-called voids, between the constituent fragments of 
imperfectly compacted rocks, such as sands, gravels, sandstones, conglomerates, tufts, 


PLATE 138 


aig Lite 
FeV 


a £6 eat 
ee, OR 


pets, 





A. Eel River, near Ferndale. Cracks in flood-plain, A. 8. E, 





B. Eel River, near Ferndale, Cracks in flood-plain, A. 8. E, 





re 4 
+ a 
a % 
é ‘ 
7 . + 
. - t . 
~ ba 4 4 ‘ 
Fi t 
i ” fi. 
“6 ‘ » 
é " 
! 
\ 
as 
‘ 
’ 
+> . 
‘ 
’ 
7 
* M 
< 
* 
? 
’ ; 
] 
- ae eee ‘1 5 Pe: » 2%. Aig ns Sa , 
Ade art be eda raat: Me ee A BC el we NY. Py ot as marge ee eee a 
\ { = 
i) ; 
re 
ae. 
a ~ 
1 
* 
1 
oe 
. 
F 
* os 
s \ 
e » 
Tiny * 
' . + 5 
t 
* > = 7 
’ 
Ps , 
4 i iy 
a ! 
‘ “y = 
7 ra 
. + 
- g 
* ‘ % « 
' j * - Te : 
A ie - 4g Psst 
Bae oS tated dey Mead 25 Mae mn Sinn in menial baal meme part a hiatus keine Shag maken sae a a 





139 


PLATE 


A. Russian River west of Windsor. Cracks in flood-plain. 


C. Fissures in alluvium ; Tevis ranch, near Alma. 


R 


8. H. 


LH. 8. 


B. Russian River. Cra 


D. Upheaval of bottom of 


artificial lake ; 


Tevis ranch 


ck in flood-plain parallel to river. R. 8. H 


near Alma, 


I 


H 





8. 





Oe ge Ue ceengeoen S 


% 








“ 
j 
1 
\ 
; 
a 
4 : f 
7 ‘ 
” 
, Lf J 
* 4 
, 
vi 
. 
* y 
bg 
Pm 
‘ e 
; i a 
. 
be ° 
. ‘.-, a 
‘ Dd & 7a = a cue 
P a5 P he 
. + 7 = 
2 es ; Re 
‘e 7) 71F - 
; ee) 
‘ Mes BS a . 
’ “ f Us “iy 
a = 7 
> 
’ 
4 
* ' ie 
3 7 
5 ‘ 
: 
4 A, 
‘ 4 


PLATE 140 





B. Secondary cracks in alluvium on banks of Coyote Creek. Per J. C. B. 






‘ ’ , © by we « 
A 7 
‘+ - 
. « j — 
> 
‘ 
a e ce 
° 
% - 
* 
" — - ore Soy mee Fyn el eds a ems ee oge llene abana Mental 
a wy , 
ae 
) 
| 
! 
f 
’ 
z ~ 
j < 
' 
~- 
: iv 
OF THE : 
soe : 
’ + 
‘ } ; ’ ‘ 


» 4 . 
‘ 
x0 
se ae 
® ; 
; 
‘ 7 
, ‘. ‘ 7 
* ; = ‘eke 
‘ : : te 
‘ , ‘ 
; « ' 
fA ¢ - ¢ 
. ; As : J ey ie h ¥ gr 33. 
q . pea 
LP 
, La 
a » - ie 
fi 2 a 7 rit. 
geek + 2% 


PLATE 14} 





A. Concentric cracks in ground around an old alkaline spring, 1.5 miles north of Livermore. R. C, 





B. Secondary crack, with drop of 7 feet, in alluvial flood-plain of Pajaro River. G. A. W. 





MINOR GEOLOGICAL EFFECTS OF THE EARTHQUAKE. 403 


etc.; (2) the cracks and fissures which traverse the more firmly compacted forms of the 
same rocks, or others, such as granite, lava, etc., which occur only in a solid or coherent 
condition; (3) the vesicular spaces and tunnels of lavas, and (4) the spaces of dissolution 
which occur frequently in relatively soluble rocks, notably limestone. The occurrence 
of water which does not permeate the rocks nor flow thru them, but is contained in 
small discrete cavities in rocks, such as the liquid inclusions in igneous rocks and in the 
constituent minerals of sedimentary rocks, is here ignored. Thruout the Coast 
Ranges of California, limestones are not abundant and spaces of dissolution are believed 
to have played no part in the changes which were manifested in the behavior of springs 
and wells. The same remark holds with reference to vesicular and tunneled lavas. 
These changes were thus confined to the voids of porous and usually little coherent rocks 
and to cracks and fissures which traversed the coherent rocks, whether porous or not. 

In the discussion of certain earth-flows in the preceding section of this report, the 
initiation of which is ascribed to a sudden accession of water from the underlying for- 
mations, attention has been already directed to an extreme phase of the disturbance of 
the normal conditions of the ground-water. In those cases the ground-water was sud- 
denly expelled or squeezed out of saturated, incoherent formations at the time of the 
shock. They are extreme manifestations of a tendency which affected the ground 
water generally thruout the disturbed region. In this connection, it may be well 
to direct attention more particularly than has hitherto been done to the behavior of 
water contained in the alluvium of the river-bottoms. One of the most common phe- 
nomena in such situations was the expulsion of water in jets from apertures which sud- 
denly appeared in the flat-lying ground. The water was usually thrown into the air for 
several feet; in some cases it was reported to be as much as 20 feet, and the ejection 
continued for several minutes after the earthquake. The continuance of the ejection 
after the shock indicates that an elastic stress had been generated in the saturated ground, 
which thus found relief in the expulsion of the contained water or that there was a 
gravitational settling together of the material, which diminished the spaces occupied 
by water. The vents thus established were very numerous, and were in many instances 

closely spaced; more frequently a few to the acre, and occasionally isolated. These 
vents were easily recognizable for weeks and even months after the earthquake, in the 
form of craterlets. The water in its passage to the surface brought up considerable 
quantities of fine sand, which, from its prevailingly light bluish-gray color, was evi- 
dently derived from considerable depth. On the flood plain of the Salinas River, the 
sand was recognized by the people of the neighborhood to be the same as that of a 
stratum of sand pierced by wells at a depth of 80 feet. The craters were usually dis- 
tinctly funnel-shaped and were rimmed by a circular flat ridge of sand which, by 
reason of its light color, was in marked contrast to the surrounding surface. They 
varied in diameter from 1 to perhaps 10 feet. In some instances the funnels were 
several feet deep; in others the feeble action in the closing stages of the eruption had 
caused them to fill up with sand. They were quite analogous to the craterlets described 
and pictured in Dutton’s account of the Charleston earthquake.' (See plates 142, 8 
and 143a, B.) 

These craterlets occurred on practically all the saturated alluvial bottoms of the 
streams within the zone of destructive effects, and also on the tidal mud flats of Tomales 
Bay. They are significant of the compression to which such water-laden, incoherent 
formations were subjected by the passage of the earth-waves at the time of the earth- 
quake or by the consequent settling of the ground. They thus afford us, in part at 
least, a key to the behavior of many springs and wells. Most of the springs of the 
Coast Ranges are in solid rock, though they may emerge on a hillside mantled with rego- 





+ U.S. Geological Survey, 9th Ann. Report, pp. 296-298. 


404 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


lith and soil. Such springs, as a general rule, had their flow increased at the time of 
the earthquake. ‘The tendency to compression in firm rocks would not be so effective 
as in the case of noncoherent sediments, but it would make itself manifest in the gen- 
eration of an elastic stress which would die out and merge with the normal gravitative 
stress very gradually. ‘There would also be an effective tendency to bring together the 
walls of cracks and fissures whose planes lay transverse to the path of propagation of 
the compressive wave. Both of these tendencies would make for an expulsion of the 
water. The expulsion could not, in most cases, be effected suddenly, however, owing 
to the great frictional resistance; and simply resulted in an increased flow of the 
springs at the surface, which would continue during the life of the abnormal elastic 
stress. The duration of this stress appears in some cases to have lasted but a few days; 
in other cases it continued for 2 months, as inferred from the abnormally large flow of 
the springs. This variation would depend on local conditions, such as the superficial or 
deep source of the water, the character of the rocks, the degree to which it was seamed 
with cracks, ete. 

This same general explanation would apply to artesian wells, in which the water 
acquired and maintained an increased head for some time. In some such wells, where 
the water stood normally at some little distance below the surface, it overflowed and 
flooded the ground in some instances. In other cases, where the supply was not arte- 
sian, but shallow wells reached the ground-water, the level of the latter rose. This 
general tendency was complicated in some instances by other effects of the earthquake. 
Several surface wells had their level lowered, and others went dry. This sudden drop 
in the level of the ground-water can be explained only by a sudden draining off of the 
underground waters to lower levels, and this might be effected by the opening up of 
the ground superficially, in consequence of -the shock. A similar explanation would 
apply to the few springs which had their flow diminished or cut off altogether. This 
draining off of the waters of higher levels would also augment the flow of springs and 
wells at lower levels and may in some cases have been the principal cause of observed 
increases of flow. The noteworthy case of the spring near Ukiah, described below, 
which ceased flowing and remained dry thruout the following summer and fall, but 
resumed its flow with the advent of the winter rains, suggests that the fissure in the 
rock from which the spring welled served as the limb of a siphon and that the water in 
the siphon was drained off in consequence of the agitation and opening of the ground 
at the time of the shock. The winter rains refilled the siphon limb and so brought 
about a resumption of the flow. 

One of the most common reports regarding the shallower wells was the roiling of the 
water by the admixture of earthy matter, doubtless due to the agitation of the ground 
and the loosening up of.the incoherent material at the bottom of the wells. 


RECORD OF SPRINGS AND WELLS AFFECTED. 


A brief and partial record of springs and wells affected by the earthquake follows: 

Montague, Siskiyou County (C. H. Chambers). — A sulfur spring was formed at a point 
2 miles south of the town of Montague. Hot water ran from it for 2 days, after which 
it cooled off. A soda spring 9 miles east of the town doubled its flow. The water of 
many springs was muddy for several days after the quake. 

Denny, Trinity County (P. L. Young). — At a small quartz mine near Denny the shock 
doubled the amount of water flowing from the tunnel. 

Peanut, Trinity County (Mrs. E. Diller). -—'There was an increase in the water in the 
ditch which comes from a small gulch. The increased flow had not diminished up to 
May 6, 1906. 


PLATE 142 


ee o 





B. Craterlets along fault-trace on sand spit at mouth of Tomales Bay, R. 8. H. 





















‘ , 
; a 
= 4 cy - Le 
; te 
j* pant ae 
; x v & 
eee _ ‘ 
a’ a 
i eae, 
~ 1 . 1 ’ ~ a 
res a Sf ice } 
° 2 te 
ay Tot (  &' 
Py “ y i slg od i > 7 
“ : ““ 
- it r 7) ; 
7 : 
id ah 
4 2 
abi 7 A 
t <A 
‘ 7 z 7 
. 
‘ 
‘ 
ny 
MF 
7 
-* 
14 
c 7 o 
ie 
¥ . De Diet 0 ria aes a 
hy » A i Ae | (0 - 
Eng ee 1 op? Se ‘ 
; : Moa. ceoe ole eee 
5 {oe ; 
a F ‘ » Md 7 
. 


ay 
we ty iste ee ' 
: ‘ ay a =a, 5 es + # . ‘ 


a are 


> 
ae, 
¥ . 
as 
Sah 
od 
id 
ra) 


143 


PLATE 


: 


b 
% 

L 
t _ 





C, B, 


A. Craterlets in fields near Milpitas. Per J 





Per J. C. B. 


Craterlets near Watsonville. 


B, 


a 
kor « 
‘ 


rire 





») 


MINOR GEOLOGICAL EFFECTS OF THE EARTHQUAKE. 405 


_ Briceland, Humboldt County (J. W. Bowden). — The pressure on the flow of natural 
gas was doubled in the vicinity. 

Covelo, Mendocino County (EK. 8. Larsen). — Some springs and wells in the vicinity 
went dry, while others flowed more freely. 

Laytonville, Mendocino County (A. S. Eakle).— A sulfur spring had its volume of 
water increased at least threefold by the shock, according to report. 

Mendocino, Mendocino County (O. H. Ritter).— Wells in the lower part of town 
became full to overflowing and a heavy seepage of water was observed in the yard of 
the Alhambra Hotel. 

(W. Mullen.) —The flow of a number of springs was increased. 

Ukiah, Mendocino County (S. D. Townley). — The water in the well at the Observa- 
tory was very noticeably roiled for several days after the shock. The Ukiah press for 
April 27 reports some very marked changes in the flow of springs near Ukiah. A spring 
near the KE. Clemens Horst Company’s ranch, which. supplied water for domestic and 
ranch purposes, stopt flowing after the earthquake. The ranch is about 2 miles north 
of Ukiah and a little west of the center of the valley, and the spring is in the foot-hills 
on the edge of the valley, nearly a mile to the west of the ranch. Pipes connected the 
spring with 2 tanks on the ranch, the spring having supplied the ranch with water for 
a great many years. The foreman, John Eldred, states that the day after the earth- 
quake it was noticed that no water was flowing into the tanks from the spring. Inves- 
tigation showed that the spring, which comes out of rock, was absolutely dry. Mr. 
Eldred and his men worked for two or three weeks, digging, drilling, and blasting, in 
the effort to regain a supply of water; but these efforts were futile and were finally 
abandoned. <A well 75 feet deep was dug on the ranch and a wind-mill erected. Eldred 
went to the site of the spring several times during the summer and early fall, but there 
was no water. Upon going to the place in the early part of the winter, after the rains 
had begun, it was found that the spring was again flowing with a largely increased volume 
of water. He estimated that the flow was about doubled. The spring was still flowing 
with the increased volume on March 15, 1907. 

Hemlock, Mendocino County (C. D. C. Bowen). — Some springs flowed more abun- 
dantly after the shock. 

Lake County (C. E. Weaver). — At Highland Spring, in Lake County, none of the 
springs dried up, but one new soda spring was formed in the Franciscan rocks. ‘The 
mineral springs in all parts of the county are reported to have increased in flow and 
number. The artesian wells in Scott’s Valley, west of Lakeport, have diminished in 
flow, and several have stopt flowing. Many wells have dried up, but this was not con- 
fined to any particular locality or part of the county. The shock apparently had no 
effect upon the waters of the northern part of Clear Lake, nor upon the springs in that 
part of the district. 

Lakeport, Lake County (J. Overholser). — The flow of many springs increased on 
account of the earthquake, while the flow of artesian wells decreased. ' 

Annapolis, Sonoma County (G. W. Fiscus). — Wells and springs have gone dry in 
places, and water has come to the surface where there was none before. 

Sebastopol, Sonoma County (R. M. Hathaway). — The wells in this vicinity were all 
stirred up, the water becoming filled with sediment, as tho a heavy rain had washt in 
surface water. A small brook a little to the left of a fissure in the soil on the Blundon 
place had its flow of water so increased that the owner of the place had his attention 
called to it by the roaring of the water. 

Santa Rosa to Sonoma, Sonoma County (E. 8. Larsen). — At the city pumping station, 
1.5 miles east of Santa Rosa, there are 4 wells, dug 50 feet and connected with a tunnel 
450 feet long. Within each well there is a bored well 8 inches in diameter and 108 feet 


406 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


deeper than the dug well. The water began to rise immediately after the shock, and is 
15 feet higher than before, altho the pumps have been run to their full capacity. 

The warm spring at Peters’ ranch was little affected, except that for a day or so after 
the shock the water in the spring was lower. At Conrad ranch, northwest of Melita, 
there are numerous warm springs, about 100°, all along the base of a hill, which have 
had their flow increased very much. Mr. Striddle thinks that there is ten times as much 
water as before, and that it is a little warmer. He also tells me that the flow is gradually 
decreasing again. The springs at Melita, along the north side of the hill, have behaved 
much like those at Conrad’s. I am told the creek about 2 miles to the north has risen 
considerably since the shock. 

A mile north of Kenwood there is a well which was dried up about a year ago by an 
earthquake, and had to be dug deeper. This shock did not seem to affect it. 

Glen Ellen Springs continue to be changed, usually increasing their flow, tho a few 
springs went dry. At McEwan’s Ranch, 3 miles west, both cold and hot springs are 
flowing much more water. At the State Home at Eldridge, a warm spring started about 
0.75 mile east of the town. Hot springs at Agua Caliente have nearly trebled their flow, 
and the temperature has risen from 112° to 114°. A spring which required pumping 
before now flows. 

Boyes Hot Spring has increased a little and now flows without pumping. The tem- 
perature has also increased a little. Several years ago an earthquake stopt the flow, so 
that pumping has been required until this last shock. At Sonoma the wells and springs 
supplying the city are flowing more than before. 

Veterans’ Home, Napa County (A. Brown). — The earthquake caused the springs to 
flow more fully for about 2 months, after which they returned to normal. 

Napa, Napa County (T. Hull). — In many eases springs increased their flow. 

Redding, Shasta County (L. F. Bassett}).— Some springs have been reported to have 
increased their flow and to have a lower temperature. 

McCloud River, Shasta County (Chico Enterprise). —Springs in the limestone belt 
above Baird, which were formerly cold and clear, became warm and milky. 

Allegheny, Sierra County (W. A. Clayton).— The earthquake changed the flow of 
water in mines and springs. : 

Suisun, Solano County (&. Dinkelspiel). — Mr. Miller’s gas well, 3 miles northwest of 
‘ Suisun, gave threefold greater volume of gas for 2 weeks before the earthquake than it 
did afterward. 

Martinez, Contra Costa County (R. Wulzen). — Alhambra Creek is said to have risen 
2 feet after the earthquake. A small stream to the east of the town, which is usually 
dry by May 1, now has considerable water. The same is reported of another stream 
south of town. A well in the vicinity, in which the water has always been several feet 
below the surface, is reported to be filled almost to the surface. 

Stockton, San Joaquin County (R. Crandall). — An old disused gas well at the City and 
County Jail had a flow of water started in it by the earthquake. This flow continued 
for about two weeks, after which time it began to diminish. In a gas well, at the City 
and County Hospital, both the gas and water flow had been doubled and had continued 
so up to the time of my visit. 

Ripon, San Joaquin County (T. H. Wren). —I have 18 acres of alfalfa land, which 
watered with an inch less water over the head-gate in 1905, in 17 to 20 hours. This 
year it took 25 hours to water 18 acres, all conditions being the same as last year except 
that the land was more packed and should have watered quicker. Others have made 
the same observation. 

Sunol, Alameda County (R. Crandall). — The level of the ground-water around Sunol 
was affected considerably. In most of the wells the water rose, some overflowing for 


MINOR GEOLOGICAL EFFECTS OF THE EARTHQUAKE. 407 


a short time. The postmaster gave 4.5 feet as the measured rise of the water in his well. 
The spring which furnishes the town supply is said to have been diminished by one- 
fourth of its flow. ‘Two other changes in water supply were reported: one being the 
starting of a new spring near one of the western Pacific camps in Niles Canyon; the other 
the rejuvenation of an old sulfur spring near Sunol, which had not flowed for many years. 

Calaveras Valley, Santa Clara County (G. F. Zoffman). — The springs near Mr. Robert 
Ingleson’s house, in section 22 on the ridge east of Calaveras Valley, became muddy 
after the shock and remained so for two or three days. The volume of water discharged 
by the springs increased to about four times the usual amount. 

Alvarado (KE. W. Burr). — At the Alvarado Sugar Mill, in several wells, formerly flowing 
artesian wells, the water-table is now a few feet below the surface, the water-level having 
risen at the time of the earthquake. In the accompanying table are given the heights 
of water in a number of wells about the mill, referred to an assumed level 30 feet above 
an assumed base. ‘These wells were observed daily before and after the earthquake. In 
most of them the water suddenly rose. The readings show that in a few cases the water 
rose from | to 2 feet. A well which used to be considered nearly dry began showing daily 
fluctuations, overflowing nearly every morning for some weeks after the earthquake. 

The figures here given are for measurements made on April 9 and 14, preceding the 
earthquake of April 18, 1906, and the measurements made on April 21 and 28 of the 
same month, and May 5 subsequent thereto.’ 


Heights of water referred to an assumed level 30 feet above assumed base. 














hye etn eck: “April 9. | April 14, .| April 21. | April 28, | May 5. 
1 470 22.89 24.81 26.14 26.31 26.56 
2 Shi be 26.64 26.81 28.14 25.48* 28.23 
4 318 26.22 25.47 28.05 27.97 27.30 
4 402 1) 26,02 26.87 28.37 28.20 28.28 
5 405 26.67 28.17 28.34 28:20 28.42 
6 402 26.70 28.28 28.37 28.03 28.45 
ef 399 26.79 26.87 28.45 28.04 28.45 
8 45 26.79 26.87 28.45 28.04 28.45 
9 544 25.36 25.36 26.69 26.94 ZiaG 

















* No. 2, April 28. House pump was taking water from this well when measurement was taken. 


San Francisco Peninsula (R. Anderson). — Thruout the central portion of the San 
Francisco Peninsula, the chief geological effects, aside from the actual displacement along 
the fault and the slumping and settling of alluvial ground, were the increased circulation 
of water and its discharge at the surface. The normal flow of water from springs was 
much disturbed. The water was usually muddy or milky. It is reported to have flowed 
salty from one spring for 2 days after the earthquake; after this it returned to its usual 
purity. Streams were considerably swollen temporarily, and water frequently came 
to the surface where it had not made its appearance before. 

(R. Crandall.)—At Mr. Ebright’s place, at the lower end of the lake in Pilarcitos Can- 
yon, the spring water used for house supply is said to have been milky white the day 
of the earthquake. At Byrne’s store, on the Half Moon Bay road, 0.5 mile west of 
Crystal Springs Lake, it was reported by the keeper that the water from their spring on 
the day of the shock was muddy and was not tasted; on the second day it had a very 
salty taste, and on the third day was again normal. 

Santa Clara Valley (J. C. Branner). — At Menlo Park, a mile nearer Fairoaks Station, 
an artesian well flowed faster after the shock. At the Seale place, on the Embarcadero 

1 Since the wells in this district fluctuate in level with the rise and fall of the tide in the bay, a cor- 
rection would have to be made for this influence before the effect of the earthquake upon the under- 


ground water could be inferred from the figures given in the table. If the hour at which the level of the 


water in the wells was measured is known, the correction may be ascertained and applied at any time. 
INNO. AR 





408 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


road, from the railway crossing at Palo Alto toward the Bay of San Francisco, a well 
was reopened. Other wells showed an increased flow and brought up sand. At Guth 
Landing, and southward along the road into Mountain View, the flow from bored wells 
had increased. A wind-mill which had for years pumped water from a well was no longer 
necessary, but the artesian water was muddy. At the Ynigo Ranch, 3 miles northeast 
of Mountain View Station, there was an artesian well which had, before the shock, flowed 
slightly or not at all, and a wind-mill was used to raise the water. After the shock it 
was found that the casing had been shoved up 2 feet, damaging the pump. The flow 
of water was increased, and black sand was brought up. Another well at this ranch 
was unaffected. Along the Jagel Landing road, 2 artesian wells had increased pressure 
after the shock. An old artesian well filled with stones had begun to flow for the first 
time in several years. 

(H. H. Taylor.)-——-The water in an artesian well 215 feet in depth, near Millbrae, was 
roiled by the earthquake and remained so for several days. 

San Jose, Santa Clara County (G. F. Zoffman).— Water and mud are reported to 
have spurted from many artesian wells. 

(W. S. Prosser.) —A well near San Jose was reported as having increased in flow the 
day before the earthquake. | 

Gilroy, Santa Clara County (M. Connell). — It is reported on good authority that at 
Gilroy Hot Springs the temperature of the water rose nearly 10° and the flow increased 
to 5 times the usual volume. 

Bellvale, San Mateo County (Miss L. E. Bell). —Some springs dried up and others 
broke out with a great gush of water, where no water had flowed before. An oil well 
from which tepid salt water, oil, and gas had been flowing since 1898 became suddenly 
dry and a similar flow began in another well 2,000 feet deep, at a distance of 600 feet 
to the east of the first well, where before nothing had been found. 

Wright, Santa Cruz County (Miss F. Beecher). — Most of the springs are running with 
a greater flow since the earthquake; but the water in our well on top of the ridge 
sank rapidly to the level it usually holds in August. The water in all wells was very 
roily for some days. 

Summit Hotel, near Wright, Santa Cruz County (H. R. Johnson). — The well at the 
summit, from which the Summit Hotel obtains its water, has its bottom on solid rock. 
After the shock the level of the water in the well rose 12 feet. 

Boulder, Santa Cruz County (J. C. Branner).— At a sawmill near Boulder Creek, 
water stopt running from a hitherto permanent spring, but another in the neighborhood 
was flowing more freely than before. 

Felton, Santa Cruz County (Miss F. Locke). — All the springs on the property of 
Miss 8. Anderson, a mile east of Felton, greatly increased in flow. 

Soquel, Santa Cruz County (W. E. Wheaton). —I have a drilled or bored well, yield- 
ing a magnificent flow of clear water. From three to four weeks previous to the earth- 
quake this 75-foot well began to show signs of agitation below the surface. Every few 
days water heavily mixed with sand and ground chalk rock was pumped up. I knew 
that something was going wrong down under the earth, owing to the action of this well. 
When the quake came, it drove both fine and coarse sand into the casing, which put the 
well out of commission entirely. 

Chittenden, Santa Cruz County (G. A. Waring). — Near Chittenden a marked increase 
was noted in the flow of oil and water, and more gas and sulfur appeared. In the neigh- 
borhood of Santa Ana Peak, the flow of springs was increased. 

Prunedale, Monterey County (H. H. McIntyre). — Water started in many places where 
there had been little or none before the earthquake, 


MINOR GEOLOGICAL EFFECTS OF THE EARTHQUAKE, 409 


Salinas, Monterey County (G. A. Daugherty). — In many places water came up thru 
open fissures; in one place about 8 miles from Salinas, the water covered about 80 acres 
of land. 

(B. M. Abbott.) — Water spouted from holes in the ground to a considerable height, 
and flooded the fields. 

San Ardo, Monterey County (G. A. Waring). — At San Ardo, quicksand was thrown 
up in a well, seeming to lessen the flow considerably. 

Paratso, Monterey County (A. S. Eakle). — At Paraiso Springs, the quake affected 
the underground waters. According to the owner, Mrs. Romie, the supply of water 
from the springs had been diminishing for some time, and the temperature had been 
decreasing. Immediately after the shock it became necessary to put in a large pipe to 
carry off the water, and the temperature has resumed its normal state. 

Lonoak, Monterey County (J. Rist). —The earthquake caused springs to flow more; 
and the water rose in some wells. . 

San Benito Valley to San Joaquin Valley (G. F. Zoffman). —In some places about 
5 miles northwest of Bell’s Station, on the Pacheco Pass road, springs were reported to 
be flowing 2 or 3 times as much water as they had previous to April 18. At a ranch- 
house 7 miles from the pass, on the east side of Pacheco Pass, the increase in the flow of 
water from springs in the neighborhood was said to have been noticeable. Springs 
were reported to have opened up considerably thruout the region around Emmet P.O. 

Stone Canyon, Monterey County (G. F. Zoffman). —In the neighborhood of Stone 
Canyon Coal Mine, the people claimed that there was a sudden rise of the water of the 
wells immediately after the earthquake. 

Dudley, King’s County (O. D. Barton). — The gas spring on sec. 22, township 25 S.., 
Range 18 E. was started into great activity by the earthquake. Formerly there were 
7 places where gas could be seen occasionally blowing off through a shallow pool of water. 
Now there are more than 50 places where gas blows off continuously. The quantity 
of water was greatly increased. Beneath these gas springs the ground is dry and hot. 

Bakersfield, Kern County (A. G. Grant). — Artesian wells 30 miles north of Bakers- 
field were rendered muddy by the earthquake. 

Gold, Madera County (T. J. Rhodes). — Several springs increased about one-third 
to one-half in volume. 

Steamboat Springs, Nevada (J. A. Reid). — At these springs the water is constantly 
boiling. For about 3 days after the earthquake, the volume was considerably increased, 
and the water became noticeably turbid with mud. On the north end of the highest 
sinter terrace, where heretofore the waters had been invariably clear, considerable 
quantities of mud were discharged. This material is now lying dry on the white sur- 
face of the sinter and is gradually being blown away. At the extreme north end of the 
active springs, where several mud springs have always existed, the change was noticed 
in the increased activity. One in particular formed a low cone of dark-colored mud, 
which is now dried and cracked. 


RECORD OF AFTER-SHOCKS, 


The list of after-shocks given below has been compiled by A. O. Leuschner from 
all reports that have come to hand. These reports include not only communications 
in answer to the three circulars sent out, but also other reports by interested observers. 
In addition many shocks in the list were taken from the separate reports printed in this 
volume. For the sake of completeness the shocks reported by Prof. Alex. McAdie in 
his monthly reports of the California Section of the Climatological Service of the Weather 
Bureau have also been included. A number of shocks have been inserted in the first 
proof from Prof. Alex. McAdie’s Catalogue of Earthquakes on the Pacifie Coast 1897- 
1906.1. It should be stated, however, that this list by no means represents a complete 
enumeration of all after-shocks felt in California since April 18. In general, it may be 
said that the list becomes increasingly incomplete with the lapse of time since the great 
earthquake. This is particularly due to the efforts made by some of the newspapers 
to suppress all news regarding earthquakes in California. The list may be considered 
complete only for Berkeley, California, where several observers have endeavored to record 
every shock. Asa rule the observer’s name is included in the last column, initials being 
used for observers who have reported more than one shock. A key to the initials is 
given at the end of the list. The times are expressed in Pacific Standard Time. 


Record of after-shocks. 























Day. a ae of Duration. |Intensity. Locality. Remarks, 
hm. 8. secs 
Apr. 18, a.m.| 5 18 57.... Gakzse IV 1 Berkeley :320aec0s 8. A. 

5) 10. foes yp Pelee III | San Francisco..... A. G. Mea J. G-), 

Be LOLOL : eee oe eee GOVE See ree: Feeble, A. G. McA. 

Lge eae Se PEs Ill AG jee eeatee? Feeble, A. G. McA.; J. G. P. 

By pa Nags a Bee Ill Berkeleyie se soe A. G. McA. 

5 OAT eee es ee Ill Hureka S2o0..4. ee Northwest-southeast followed 
by a side  cross-motion, 
Persons in beds resting east- 
west not awakened, A. H. B. 

) 20045255 if he 13 Berkeley*.sS.22-e- mks 

5 26% Sees. Nee eee Yas ae San Francisco .... | Feeble, A. G. McA. 5 

Dae teen. Aa lon tl roto Se IGP! 

bes Blbse Oe ae + aE Berkeleya.. seer S. A. 

ip tey WRN 4 I ees Il Ose eter 

DOO) s ss See eee one ee Humboldt Lt. Stn 

5 34 40 De ae Il Berkeley .......-- S. A. 

5 35 Ol 1eSee II CO. acres S. A. 

DO oe ns eee et CO ere S. A. 

5 89" S2 2 ee eee ) i G0: ee ee S. A. 

BASS coe Ce os yey San Francisco .... | Feeble, A. G. McA.; J. G. P. 

2 AS <o0neee Bn een Ill Berkeley... 3-2 e=- Two separate jerks, 8. A. 

5 AS core eyes cee ae ee Phoenix (Ariz.) ... | Slight. West to east. 

5 59's lS eee ee eee Il CO. ace ese S. A. : 

6 00). 22 cec We Sono eee San Mateo Point. 

6 06.2 send eee oes eas San Francisco .... | Light, N. E. 

GelOesbeeee ths see Itt Berkeleyas. eer ne 2max., one at 36s., one at 
41s.,8. A 

O225 el saaee 2 ee IT Oye osc. A. 














1 








mithsonian Miscellaneous Collections, part of vol. XLIX. 
410 


RECORD OF AFTER-SHOCKS. 


Record of after-shocks — Continued. 


411 


























Southampton Shoal 


Mt. Hamilton..... 


Day. B sg ed of Duration, |Intensity. Locality. 

hoo ine <8 secs. 

reer ee kl GOW. 7 |) 2. er esc eee. San Francisco .... 
Crore ee see ee ee I-I Mt. Hamilton..... 
OFA 22 as ee mes eae 28 eee ee San Francisco .... 
6 44 11 Geese IIl— Berkeleyge 2.4255 
85325) Snes th I ey Oe eel | ar ae Mt. Hamilton..... 
Or4G: 34 tena eee II Mt. Hamilton..... 
OLOU cae roan tate soe IV Scott’s Valley .... 
CLovee ie are IV clare ee tere 
GRD pemee on cles cre ene ee Ue I Se Oe ee ee iio 
(Pod UU hs 2 tiers ase Ses ee ale (Te Cloverdale....-... 
ae O dae eee |e ee IV Scott’s Valley .... 
CF PAV bese: vege ar ise Oe ea eee Sausalito. 2).coee 
i, Byte ely | eee 1V Scott’s Valley .... 
fa eo Se, te te en (rn Sacramento......- 
bo dl OPE ea a 2S: 1 Bonita Pt. Lt. St.. 
SUaO (ee ceed eis ae ot Re ee Yerba Buena..... 
fo} AA De tees a Sb Ao Mile Rocks....-... 
See ee Te le eee Mare Island ...... 
sobs BIS Coie ie eons flan ay A | ee AT MIOCI eee ae. 
8 14 14 LOR ee IV-V | Berkeley ......... 
Sera 27 weve |e yon es. IV-V fe oer ee me 
8 14 28 

to } Vee een | Oars e San Francisco.... 

8 14 33 
SOULE rel OO aeyerees (ers ai cos II Mt. Hamilton .... 
8 14 45. en etal | Aterees Sacramento....... 
SLD ees meer | Pomk ee ML ey oe PGA tradooe a. ese ets 
Seiya eres beh eae A Riese ie Oakland occ 
SLO Reee rea ee Sale 2 =" Yount yillessen sees 
SES ees. Lasse? V Mile Rocks....... 
Selbek see, Dapee: V San Francisco 
SESE ee Alte III GOs Fics ies 
ShG eee pews Be WO; ee ee 
8 19 20 pubes V Oakland's eases 
S200 Werte dacs eee IV Scott’s Valley .... 
PPA pee See || Me IV Ow er ae 
SusQiese eee a ee ee ee 2 II PLnGlumMine == eee. 
S25) Weer oie Lake hae all SltockLOn = - a 
SA 2 ee See ee ak San Francisco .... 
SV 5 parent See vee IV Scott’s Valley .... 
SPOS ee es ee IV lapel dene Ae ae 
Oe 4 re we 2 ee ee toe San Francisco ....- 
OPLG 5 22ee— A eee Vina Mt. Hamilton..... 
OS ee ee ie eee IV Scott’s Valley .... 
ORO ora. se eek IV GGsn.n wee 
CeO se eel) « 1-2. (a SOS Mare Island...... 
WP. aE Mere Ee IV Scott’s Valley .... 
OL 2G are at cee See eee San Francisco.... 
OP 2 Gm) Open LO e cr 2 II Berkeley ......-.. 
OU ZS Soe Qe ees Ill San Francisco . 
9 
9 
9 
9 




















Remarks. 





Light, N. E. 
BG, A. 
Light, N. E. 


F. L. 
San Francisco Light, N. E. 
Slight shock about 7 a. m. 
Be 1. 


FL. 

Slight shock soon after 8 a. m. 

Nearly vertical; toward NW.; 
no tremor, just a jar; 1 max. 
strongest at beginning; no 
clock stopt, no sound. 

Light. 

Smart 

Slight shock. 


Was looking at watch when * 
shock began, S. A. 

At Students’ Observatory, A. 
QO, L. 





Sharp twisting motion, A. G. 
McA, 
A. M. H. 


Severe. 

Strongest at middle, sound 
like cannon shot, following 
beginning 1s. Sharp. 


Northeast to southwest; 15 ad- 
ditional shocks by 1 p.m., 
duration 2-5s.,east to west, 
III-IV. 3chocks between 1 
and 3 p.m. 5 shocks between 
Apr. 18,3 p. m.,and Apr. 19, 
6 a, m. 

Howls 


About 8" 30™ a.m. 

Very light. 

N. E. 

Heals 

He Uy 

Sharp and short, A. G. McA. 
KOGA, MH: 

JRE Abe 

1th, Ub 


Toderate, A. G. McA. 
S. A. 


N.-S. Horizontal tremor 10 s. 
before, 1 sharp shock, rumb. 

One other between 6" 45™ and 
85 15™, R. G. A. 

LE be 

aby 



































Remarks. 

















N. E. 
Ewing seismograph by R. T. C. 
and S. E. 


Slight (about 10.~-). 


Not very perceptible, but stopt 
some clocks. 

Increasing intensity with prin- 
cipal disturbance near mid- 
dle of series. No clock stopt, 
rage Bae 

ete motion east-west. 


Two distinct vibrations from 
north to south. 

Felt by Mr. Legler at Pt. Reyes, 
with whom I was talking 
over telephone at the time, 
about 3 s. before felt in 
Farallones. J. A. Boyle. 

Ewing seismograph by R. T. C. 
and S. E. 


Slight tremor, followed in 
about 30 s. by hard shake 
of several seconds. Fully 
the fifth hard shake since 
5! 13", F. L. 

West-east. Apparent direction 
-east. Tremor 5s. after first 
shock, no noise. 


Moderate, A. G. McA. 


| at 

Distinctly felt on ground and 
caused falling of loose parts 
of buildings. 

Moderate, A. G. McA. 

Ewing seismograph by R. T. C. 
and S. E. 

Students’ Observatory, A.O. L. 


Longer than usual, F. L. 
Nearly vertical. 
F.L 


Southwest-northeast. No clock 
stopt, 8. D. T. 

Oscillatory motion. 

Caused some clocks to stop; 
not all. 

Moderate, N. E. 

A. M. H. 

Vertical, K. B. 

Harbor Lt. St’n, Alameda Pier. 


Ewing seismograph by R. T. C. 
and S. E. 

Faculty Club, 8. A. 

Bi LON: 

A. G. McA. 

Very light, A. G. McA. 

A. G. McA. 


412 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
Record of after-shocks — Continued. 
Day. Berens of | Duration. Intensity. Locality, 
lee hast, HI secs 
Apr. 18,a.m.| 9 4022.2. 1 iain Scott’s Valley..... 
9 48. ee ee ee eee Oise. Neace ee 
9.48.4 Sa oe eee San Francisco.... 
9 51) Soak alls csc ae ae Berkeléyecaencce- 
9 54 30. Le ere III San Francisco .... 
10:62. eee ee eee Lakeports..0-..3- 
10 Or eee eee eee Oaklandes 2. 
lO net ee eae lees Upper Lake...... 
10 04 39.. (KES ese IV Winah = ese se eee 
10:05. Seale IV Cloverdale... ....- 
10: O53 oe eee eee San Francisco.... 
10s 05¢4'7e- ee) een nee oe Point Reyes...... 
10 05° 50 sl ao eee Farallones........ 
100602925 e) eee ee eee Berkeleycs.jce< ace 
OO A aesa8- pene Bf San Francisco.... 
10°22: Jess 4 eee ee ee Scott’s Valley .... 
10 (30 2. osc 15.2c.cuuy ower Southampton Shoal 
lO jG cee i Beg II San Francisco .... 
10: 50¢ 32 5..2 6) eee ees GOs sexes ose 
LONSORS0re irc a Os8 2 ee oee 
U1 acc aceees | dey aes Scott’s Valley .... 
11 0035 esa eee V S. F. Peninsula... 
14. 06 Seen ee tenes eee San Francisco .... 
Ti OG3 232 yee 5 eo. eee Berkeley .......-- 
11-06. 2754 280 eee 76 (oh ees pete * 
C1):07 230-2) Ge ee Antiochies ee ssse- 
11 O82 eee eee ah Aig! San Francisco .... 
A 3 ee Scott’s Valley ..-.- 
Li ibeeee eee 2x e- 2 Bonita Point ..... 
1622 Se sae 60.3222 See Scott’s Valley .... 
11 36:00; 35 eee Ill Wiciah see ate 
11 139 4. eee eee Ill Cloverdale. j-....2 
11 (40 J scncee Ul oe ee Upper Lake...... 
1 427 Ree al ee tad San Francisco .... 
[1 S3e34 ea eee Il Mt. Hamilton..... 
11 53:3 (ee eee ee I ote 
Apr. 18;pm,}\12 03¢207 2.2 eee Oalklandesse-—-—e- 
12.03 2.245. 1) eee San Francisco .... 
12. 03:-43.225 Wl 22 o. 2 oe eee Berkeleyicco5--2.- 
12 05044. PA ee II+ ole eon 
1D O88 52 ice. StS aeaeeen AN eee GO-2e ace 
12404. 53 see Ate Iil San Francisco 
12 DL ces. Sele A a ee felon one ee 
122.13 eee oe ye II GO con eee eet 
1225 eee Nee eee Hurekatessesocre 

















Slight and of short duration, 
A. H. B. 















RECORD OF AFTER-SHOCKS. 


Record of after-shocks — Continued. 








413 















































Ds ring of | -Duration. |Intensity. Locality. Remarks, 

hm. FA, secs 
A prels, mmo) 12°31. cau <oa. III | Los Angeles...... 

bp OD ft. cto os wate ot «2s Scott’s Valley .... | F. L. 

LED Oi este 7 ee it San Francisco.... 

Lee ey ae ae | a eee ee bee! Scott’s Valley.... | F. L. 

Spel Need Ne ees al fe cans Wright’s Station.. | Slight. Four miles south of 
Wright’s Station. 

Bsus habia Bue Loy ae IV S. F. Peninsula... | A little before 2 p. m. 

MOR GEM wees Ut cdek dc Humboldt Lt. Stn. 

De2) eo caees Dae di awe = Southampton Shoal) Vertical throw north-south 
tremor 20s. before; no noise. 

oe Te (Oo en, ere Bteckton:..2+. <a. Very light. 

ee Otaerta tee 2 3 Selina £0 Scott’s Valley .... | F. L. 

Da Dian Gees pe | Ue Mare Island...... Slight. 

ie Devel (eter Sele oes ij Mt. Hamilton..... 

Bee e ea ONO sewn aie |, < steer San Francisco.... | Very light, A. G. McA. 

LVS ) eas eee ene Berkeley ......... Ewing seismograph, R. T. C. 
and §. E. 

A OA ae ge Lee Ill San Francisco.... 

iO aaemed. MA ocr ous, |. netee's POR IUEIES ne 5 eg voce 

Berd tae Wei coe Wb. da als Los:Gatios. oo... <. oes ER 

i ES | ane ae Dakland...2..25.. Alameda Pier. 

pe Tee en ane Mare Island ...... Slight. 

EOS es Som Boos. ct Nhs ee San Francisco.... | Very light, A. G. McA. 

2 AosaOcetecin wots He. III | Mt. Hamilton..... A. H. M. 

DepeenU seae Rwcavcs b acece Berkeley ......... BOL aN, 

RE SE, os es Sacramento....... Very light. 

Soe seers Wace fe. WN) adewe IMIOGR 2 eat ee ae 

MiP Pela eA Sah ew asc IV Scott’s Valley .... | Extra hard, stopt clock hang- 
ing on wall facing south, 20” 
pend. Stopt clock facing 
NW. by WNW., pend. about 
Bry Beds 

RENT Sy Sn Tee 4 miles south of | Slight. 

Wright’s Station 

510 eed VI EW Oleh tee nine tee Stopt clocks (counted 35 
shocks up to April 30),S.D.T. 

2 OW awe Ske 2 Roe Ill San Francisco 

ASUS Se a re AUS Ss 5 a ee 

2 ae eee ee Log Gatos. io. oF: ip Pay 

DOO bie est Bo ues Ill San Francisco .... 

Dead lactam aise 35 a VI LC Gi ae 

vt ee III-IV| Scott’s Valley..... Extra hard, F. L. 

2e40r. neeeg | ec. 0.0 Pollaits oS SUEUR roreieaae 

7 ee eee Reapers & Scott’s Valley .... | Lighter, F. L. 

ZO Seperate. | oc dG ase Lighter, F. L. 

Oe A RO I perme V i068 GALOR.<. . 2. o. Little if any vertical move- 
ment. A muffled sound, like 
distant blasting heard in a 
mine, was noticed just pre- 
ceding minor shocks which 
followed,. including that 
about 3 p: m., 1. H.S. 

ce Oe ar Ose ees IX-X | Raleigh .......... Three shocks. 

LA es ee Lame feat tees ste Ballast Point...... Vertical prop. SE. Increas- 
ing in intensity, strongest at 
middle. Clock stopt at 
4h 28™ 15* pend. 18”, facing 
E. 

ES BR NW cn 3's cae JL scien MOMCCUl. 5. 00 «6 

4 29 45.. BU eieces IV-—V | San Diego........ Northwest and _ southeast. 
Strongest apparently at be- 
ginning. Clock not stopt, but 
disturbed, losing about 1 m.; 
pend. about 26”. No sound 
phenomena. 

Avo ie kaetre mh <i ss.cecdwatased San Dievo2: gee. Heaviest in 15 years, north- 
east-southwest. 

ROU capstan Sas. oie II RAMON... 6ss2e8e A few seconds. 

Aes erere cree iI tate III San Bernardino... | Southeast. 



























































414 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
Record of after-shocks — Continued. 
Day. 5, Seaki of Duration, | Intensity. Locality. Remarks. 

bh. mas secs 

Apr.18,p:m.| 4°30....2-2 |) wesdeee Pees San JuanCapistrano| Slight. 

4 30....... | ..:..-- | ....2 | Hemet, Riverside. | Shock increasing and dying 
away. 

4.80). 520 23 A eee ee Vumae(Ariz.) eens 9 or 10 distinct shocks, slight 
rolling from east to west. 

APSO. Sees eet acne one IX «| Brawley; -.c-. see Northwest-southeast chimneys 
fell to west. Movable ob- 
jects in bldgs., thrown west- 
east. Oscillation followed 
by tremors. Clock stopt at 
45 30™, facing south. 

430 seems Few: ai? 9s.u. Ballast Point..... North-south. Horizontal. Clock 

stopt 42 30™, facing NW., 
pend. 177. 

4°50 See ae Mleoe es Seen eee Oskiand. 5s ¢00- 4% Alameda Pier. 

4 50 38.. Liat eaweetee Berkeley ......-.-. Two tremors within 1s.,B.L.N. 

45 Se ee ee el eee ee San Francisco.... | Very light, A. G. McA, 

A 52 see Vee ee ee ee Yerba Buena..... Light. 

6 02 42.... Danes Il Berkeley ........: 8. A. 

6 03 04. Less Jal GOins nose se ee S. A. 

G12. Ss. aes a eee Yerba Buena..... Light 

6 45.5 oh. cser | ese e se og eee Antioch as.2-ese- 

6,10 tees alee ee ee San Francisco.... | Very light, A. G. McA. 

G10 eae see Oa ex's ott | ee Southampton Shoal} North-south. Horizon direc- 
tion south, two light shocks, 
rumbling following shock 2s. 

6502s seal ee see ee eee Oakland 2.7. 2c252 Alameda, Pier. 

GO S1i 29-40 Se ee IV Berkeley ..2..2222 Faculty Club, 8. A. 

6551 35-457 see a laerees GO ee See Slight tremors during interval, 
B. L.N. 

Or SLEDS... a eee I-II_ | Mt. Hamilton..... 

6G 51-4588 Ss Pee II AOR eee Vertical, K. B. 

6°52). 5.222? See een eer Sacramento......- Very light 

6 63ic...2-2 | eee eee Yerba Buena.....- Light. 

Sunset !. 2a.) le ee eel eee Angel Island ..... Strong, rumbling. 

US ne eee ates 12 ee eee Mare Island...... Slight. 

( PE Tee eee Stockton.) 2% 26. Very tight. Number of light 
shocks reported for several 
days, but hardly perceptible. 

discacceeseed| sent een eee Scott’s Valley .... | Lighter, F. L. 

7 OL cn. CoS ie et eee San Francisco .... | Very light, A. G. McA. 

f 2a come ae sean mel eee Yerba Buena..... Light. 

7 25 oo. ct | eee ee eee eee Scott’s Valley .... | Lighter, F. L 

Qn10 cee oe is a doiks. fees Lighter, F. L. 

9 437 | ee 2 al eee GO.ate eee Lighter, trembling of house 
kept up for 2m. or more, F.L. 

10-3 20, SPS die sees Lakeport.....-..- Light, about 10 o’clock. 

LOSS .8 Bisco | lanes eee Scott’s Valley Sharp shock, rather long. 
Trembling of house kept up 
for 2 m. or more, F. L. 

Ul “LORSS yet ae See eee OMe See ee Trembling of house kept up for 
2 m. or more, F 

11022 50. Se ok eee Oe dO). 22 Seana Light shock, F. L. 

Apr: 10,8...) SL S30-c2 ee eee Paisley, Oregon... | Tremor. 

ey 20.2355 (aa Biveka ca. ace es Slight, A. H. B. 

307-005, £251 bon eee San Francisco .... | Light, A. G. McA. 

D aoisce de see eruy es Meee Hurek areas sees Slight and of short duration. 

GO Tizer boc Obes dns Ae Wureks.cce-s. ase Slight, A. H. B. 

6 25 10+ Se iM Berkeley ........- Time is from memory, failed to 

record shock at time, 8. A. 

aise Meare tarde 2-5 II-III | Oakland.......... | Seven shocks between 6 a, m. 

and 25 15" p. m. 
1053038755 PH feral BL yan Hureka = ree ee Slight, A. H. B. 

Apr.19,p.m.| 12 31 00 20-30.. | ..... Los Angeles ...... Increased intensity, 1 max., 
strongest at middle. No 
sound. 

12 31 41 dds. eee 





Beginning of 


RECORD OF AFTER-SHOCKS. 


Record of after-shocks — Continued. 





415 




















Day. aiatek Duration. |Intensity. Loeality. Remarks, 
ve girly HS] secs 
ITO 0 Ip ee | Ee oe Pee Los Angeles ...... Two shocks about 6 m. apart 
followed by slight tremors 
for about 1 h. 

12825 Rae oe Lo seaoae ates Pane eednones sate. Horizontal tremors 10 s. be- 
fore, increased intensity, 
strongest at end. No sound. 

VN AS ake Sees = | Rene ot ee ae San Francisco.... | Sharp, main portion with twist, 
A. G. McA. 

Qa Omeiatse sMeh we oon | 9. See Reno, Nevada.... 

ee Pe oe e lye ace Palle ee see Another shock later. 

Gl Peas Saeed ei mee 1m Sacramento ...... Seemed to be north and south. 

Bet Se, lea ccs IV-V | Hagen, Wadsworth, On east slope of Virginia 

ete. Range, Sierra Nevadas; 
northwest-southeast. During 
next 1.5 h. 3 more, G. D. L. 

RO) A ares | eee III |S. F. Peninsula... | Slight. 

Pe eee Se ee Ye dkwe Laurel Glen ...... Tremor with 2 sharp after- 
shocks. 

UR OG Se eenoan 2 So oe | oe Woke Yerba Buena..... Light. 

Mile Rocks....... Slight shocks during day. 
Lge 0. ae ee Hpesce ilitesece BNITOK aso se5 so 7M el 18h 
DELO SE eae, | Oise Vee ee PA ha ec | |r te te Southampton Shoal| Vertical; direction upward. 
Tremor, 5 s. after; 2 sharp 
shocks, cracking sound co- 
incident. 

eS es ee, ae ae an Wiketaier ed erd ce Shock too light to be felt. It 
was detected by motion of 
bubbles of latitude levels. 
The oscillation was 4 or 1 
division (N. and 8.) d= 1.0”, 
So. T, 

Gene ae aes ween see Purnekaite sc on 2 oon South-north, slight. 

ALAS COUR Sy boro allel ye San Francisco.... | Tremor, A. G. McA. 

Be) eee cele terol INORG ee a 

ice Seo ae ale ee oe eee Laurel Glen ....-. Short and sharp. 

DRO Lea ee once lk scree San Francisco.... | Moderate, A. G. McA. 

GLO se SE Nee eyes Mile Rocks....... Moderate. 

(rs Sean Saher || ede ed ORO eehor Vertical. Strongest at middle. 

(Pub sae | ae ee eee Laurel Glen ...... Short and sharp. 

SLOP atc eid os co Bal Daca Ge San Francisco.... | Moderate, A. G. McA. 

MTG S 0) Sectors eed Sk con. cicrds IN" Steiesee Tuoclummnes..o--.- About 11" 30™ a.m. 

Go ip’ Vy a tg oe eas Sa Ae ie iW Santa Monica..... | North-south. Time not accu- 
rate. 

PAS PER Be et | eaety ia (allege Laurel Glen.....-. Light. 

DELO ee ee LO oeeetere IV S. F. Peninsula... 

Del Orr rao « ae set LE One see Followed after 4 s. by another 
brief motion. 

ae eee ee isis ee III Gree oe ee Series of gentle tremors. 

ie: See ae ane re Scott’s Valley .... | Light but decided, F. L. 

12a DF Ses nl le ems alee on oe eae Barely felt, F. L. 

LOR2O serena et ers tlh ee oe (OC es pee ee 

Bh gesazat auth ei GP aie ater, [PAN et Mile Roeks....-..- Slight shocks during day. 

NW 8 Sa A ot ae oe ey ee oe ee anasto. tes os Ws. Mi. 

Ae) eee meres ee Mee ee Scott’s Valley .... | F. L. 

OMe ee as Pre San Francisco .... | Strong, A. G. McA. 

(NUL nokta | a ha Mia Scott’s Valley... .. [at re 

iso mereye stor ihteree IV S. F. Peninsula... | Shaking houses 7 s. and re- 
peated after 5s. 

oo LO ete 5s ee Soe | eeteserers Mare Island ...... T. J. J. See. 

ee Pee ee ee Sa Scott’s Valley .... | F. L. 

od yet eas ev tyelen | ae ea (ee Mile Rocks.....-- Slight shocks during day. 

Aprs22 SH We ORs Seen ee ol as et HOMO ea ceo ileus = Be 
CE ag oe! | a ee eae Scott’s Valley .... | Two shocks barely separated, 




















last continuing fully 5s.,each 
a good shake, not severe but 
steady, oscillating, F. L. 












































416 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
Record of after-shocks — Continued. 
Day. Pee of Duration. |Intensity. Locality. Remarks. 
hie ws secs. 
Apr. 22;8.m5Bc00 ruse es. 1.5... .)) eee Mile Rocks....... Slight. 

658 See es Seen | Rerteree Scott’s Valley .... | Two shocks barely separated, 
last continuing fully 5s.; each 
a good shake, not severe 
but steady, oscillating, F. L. 

(ERS eer Dore eee Mile Rocks....... Moderate. 

7:03:00 22° 2 2 ae San Francisco.... | Light, A. G. McA. 

T OS 25 eee ees Scott’s Valley .... | A mere jolt, F. L. 

11 30205.) seu or eee Saratoga ....:-..- Described as underground ex- 
plosion, about 115 30™ a. m. 

Apr. 22; p.™.| Sinus. deace nal eae he ae ee Napa Ase =. ove ae W...HoM; 

SN re Ae 3. .e eel oeeee Mile ROCKSa 2-52 Moderate. 

oe Wile et eae ee [Rae oe? Bonita Point ..... Nearly vertical. Direction N W.; 
no tremor, just ajar, 1 max., 
strongest at beginning. No 
sound, may have been blast- 
ing. 

3.18 20.2271) 602... Ill Berkeley .....-.... Tremulous motion for 5 m. 
after shock. Long duration 
of trem. motion also observed 
by Mr. Huber, who was in 
laboratory at time, weighing 
chemicals, 8. A 

3°18 22. Dems III Oakland ss -seqrece C.B. 

3 19 GRR eee) hea ae Yerba Buena..... Light. 

319° 30 22 Ass zee | | testee San Francisco Moderate rocking, about four 
waves, A.G. McA 

S'35 Heese ee eee seen ALINE So. 2. eee 

9-08.08 ee. > pra taee Wear pe Mile Rocks....... Slight. 

LO: 4.0. Sos ie iyo, eee mene AMAGS Se yee 

11] 20.2 .c S25 ana ee Scott’s Valley .... | Tremor, F. L. 

Apr. 23,a.m.| 12 05 00..- ES Nese ric San Francisco .... | A. G. McA. 

12348) eee ere SCE Trinidad Head.... | East-west tremor 5 s. before, 
short and heavy; clock stopt 
12h 48™ a. m., facing east; 
sound like thunder, preceded 
and continued during shock; 
same throughout, no change. 

12 bb 2essee 6... ore Cape Mendocino.. | Vertical. Southwest-northeast. 
Direction NE. increasing in- 
tensity. Clock stopt. Pend. 
22”, facing SW. No sound. 

110. oc stee ay es eene eeee Grant’s Pass, Ore. 

130.3220 14.233 V-VI | Eureka........... resect Stopt clocks, 
A. H. B. 

POLL tts ces 10 22356 aoe Ferndale... c.c..5 Severe shock, J. A. S. 

Daas ee ee eae Scott’s Valley Light and short, but decided, 
lice Fe 

ee ee es Il Crescent City..... West-east. 

L1G wae 2 ee Ree rs Peer teen & South-north. Woke up every- 
body, no damage. 

tLe Se eee Cape Mendocino.. 

Ds o:a ia apse Rs eat eae re ene Scott’s Valley .... | “ out enough to waken me,”’ 

L. 

OO aoe ee pI Se Bureka...cs- eo. ne South-north. Slight. 

GO w esa rampart WE Se. Merndale ot siswe ne Severe shock, J. A. 8. 

Sian en a eal Nalitigg 25 .saene 

S$ LOCO. S25 ee Ill OnklanGgssae From east, C. B. 

Ds Ln sie ofr 4 Neen Mile Rocks ....... Moderate. 

Apr. 23, p.m. 12 45, 2) ew ae ee ee Scott’s Valley Barely perceptible, F. L. 

12 48. ewe tee eee eee 6 (oe ek Pasa Very light, F. L. 

12 50. oes i en ees die wo aee More decided, F. L. 

4 OD denideee BO. oe. wae dotec nee Decided trembling lasting per- 
haps 30 s., F. L. 

SjO1e sae ame Listen igen San Francisco.... | Sharp, downward jolt,A.G.McA, 

5330. eee Salihas:: vac .tasunis 








RECORD OF AFTER-SHOCKS. 417 


Record of after-shocks — Continued. 





























Day. i hitorm of Duration. |Intensity. Locality. Remarks. 
hey ms Be secs 
Apre23,p.m.) 5 45....... Sod: Srey ee: Scott’s Valley .... | Sharp, lasting 3 to 4s., F. L. 

OOO Mercere, ||P n es Iil S. F. Peninsula... | About 10 p.m. 

LOMZ OO see ae eee S aM eter coe Mile Rocks....... Moderate, 2 max. 

Stee eae cen ae te eo hoe ae San Francisco.... | Moderate, A. G. McA. 

Acai e oa. |S Gide tees ae Bonita Point ..... Nearly vertical. Direction NW., 
no tremor, just a jar, 1 max. 
strongest at beginning. No 
sound, may have been 
blasting. 

LOCSS 742220 Gece. IV Berkeley ......... 2 separate shocks, 2d stronger, 
=. 

to ASC | nc Peas! Sas os 3 13 Bear ene 2 separate shocks, 2d stronger, 
E. Smith. : 

LO) SS GT tral s o:c.0% 10 Ill ra fs ae ae Short and sharp. Northeast 
southwest. Tremulous mo- 
tionfor6m. In bed awake, 
but watch correction uncer- 
tains We Lee: 

10.39 See-5 oe freee | ees S San Francisco.... | East-west. 

Vito) Il Oaklandsesecas= 5 CBs 

eS SE PL ee ee eee San Francisco .... | Short, A. G. McA. 

ILS eS | ee | GOn esas Tremors, A. G. McA. 

ee ee a ieee Te Ee ay Doubtful, A. G. MeA. 

ye eas 2 olny 2 5.c)4. 0°: |h 5 Sa SU CC e 

TOR Bee aoe Fam Were 10 he ies Berkeley o. 25.525 Slight continuous trembling, 
S. A. 

pre tL 1S ee tear | hse dee eh ewes San Francisco.... | Light throw, A. G. McA. 
44 5R She 82 ENTS Senora Berkeley ......... Slight continuous trembling, 
8. A. 

Corel (Vaart pen Wo 2 Mile Rocks....... Slight. 

TRE SH Sk oe GU tear hs). «acne Berkeley ......... Slight continuous trembling, 
S. A. 

LOA Sree | esctasioce. | sane oe Oakland, ..¢ 2.24. 

LIL SOE atta ce | RABE aed eee Berkeleyi-%3 22... Reported by several. Mr. 
Wood also reports shock fol- 
lowed by unsteadiness of 
ground for over 1 h.,S. A. 

IPED se ead |e tec cts II ecae Onaklan dren perm 

Apr 26, ame BEWT’ 2a. Serra) Neto Berkeley ........-. Light shock, lasted about 3 s. 
after awake, 8. A. 

A SOME eee eee. on sh Pat. ot San Francisco.... | A. G. McA. 

6 30 22.... as Ut pe Oakisnd:.2f v2.53 Northeast to southwest, C. B. 

LP ip po ee ee A’ Mills College... ... Many small shocks, 

cee eae |e iil Cloverdale........ 

“SR oty Pee) | ae A aN Mile Rocks....... Slight. 

Sete es Sa mere V-VII| Cliffs about 

Wood’s Gulch.. 

DO LZ es. PAA a V Bonita Point..... Direction N W., no tremor, just 
a jar,'1 max. strongest at 
beginning, no sound, may 
have been blasting. 

Selpiarseet ASS Se Vv 8. F. Peninsula... | Strongly felt on ground, caus- 
ing landsliding along coast 
cliffs, lasting 10s. with a 
slight repetition after 10s.. 

Pa ES pea Sheen Ill Wakland.=. s-44t2 4 abe 

Sh) eae || eee ea IN ree NADAS tote sox 228 Sharp, W. H. M 

RE epee oe Ce iges IV-V | Berkeley ......... Walking with Dr. King, not 
felt by either of us, 8. A. 

EAA bes ices ell oe eee ral Ee Yountville sec... Undulatory twist, quite severe. 

eae igi h C) ecrepere ie eiers eal) so eer San Francisco.... | Double waves recorded on 
seismograph, W. R. E. and 
A. G. McA. 

Site MS caspase eae | meee ee Oakland@s se se ecee Noticed by G. K. G. on clock 
marked U. 8. Observatory. 



































418 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
Record of after-shocks — Continued. 
Day. on Nea! of | Duration, | Intensity. Locality. Remarks. 
hi, m.. 8. | secs 

Apr;25, Dali) g05k 7540 ees oe ape II-III} Mt. Hamilton .... 

ech Oe aes) eae ge | See ce Berkeley. soe. 22 2 tremors about 5 s. apart. 
Epa . Time is of last one, B. L. N. 
3: 20 wee rea hia 5.<.2 = ee Oakland see acer Alameda Pier. 
B20 save oe aloo ae ATUIOGM 5 See eae 
ee ee ee es Mr a kas Nileas ia: bee cee Many shocks during month, 
Wee. 
Apr26, 8:00. | \Bie20 -oee ea ee eee PSUNRS Zl. sce fue 
| LO V2O SRS acct soa mec Scott’s Valley .... | F. L. 
LO%23 it on eee San WOSe.- een ae 
10 20. Se eal Mitek, oe eee Oakland... 3 055.5 Explosion? Chabot Observa- 
| tory. 
10 S338605. cece es II | Mt. Hamilton..... Jolt only, no swing, R. H. T. 

Apr: 26/p: 1m.) Sea S See oo ee eee Mile Roecks....:.- Slight. 

"5, ee ete IW Pres) ie | Saratoga .. sek Like explosion under foot, 
| | similar to shock of Apr. 22 
| at 11" 30™a.m. Light. 

| AO. ee ee eee hoes uae |, soarears b Salinas. ssa aetoae Very heavy. 

| SO sae Was haeeret= GO ee eseee 

OS35 Sarees | ad ee oN eae NilesRocks 352 ae Slight. 

Se eee ae oe 2. alas 22 recta Other shocks reported, but not 
recorded. 

O85 Olea 5 thee) Malate ats GOhs. ataae Very heavy. 

9550: senee ee ae ee Mile Rocks....... Slight. 

POPPY RC RCO Rs ore | AS ayes ih odes SNAG. ees ee Very heavy. 
ee aes ja” BAe I] Oakland 2 see Chabot Observatory. 

10 BOe sees 1) ene) Ae Ferndale ......... Sharp. 

110 80.535 .k he tee wwe i Sere Buteks «cep uwe Sharp. 

Apr, 27, ).M..\) st07 eee. seeies 4-2 0] ee eee CATCIS Or A. G. MeA, 
| 1 09 34. EY iat Berkeley ......... Rete. 

d LO. csatewAh? |. ssa. | eee Eolister ats sae 
L Lee tesa. oe: Aerts rele aes And many others. 

| 1008108 ae II] | Oakland.......... | East to west, Chabot Observa- 

| tory. 

Apr, 28,8, tia) 12° Sich escent eee ae faa. 5 secs ian a0) | SEAR cael oe 

| Apr. 28,p. 1s oh: AO 2 eee ee are ener Scott’s Valley .... | F. L. 

Apr, 29,8.™m;), 4765 ....e-e Dose els ee ee Mile Rocks....... Vertical. Strongest at mid- 
| dle, sound like cannon shot, 
| coinciding with beginning 

of shock. Sharp, following 
strongest disturbance 2 s. 
Die eee 2 = <a eee Coy eee 
Re Weide Site ss Winton Paisley, Oregon... | Milk spiltnorthwest-southeast. 
About 9 a.m. 

| 12220... ae i t-sle Seve oa PT ge Scott’s Valley .... | Hard, not long, F. L. 

Apr.29,p.m.| 4.08. 22200) ae ne OG,.e0 450 se th Hard, shook house well and 
lasted several seconds, F. L. 
| 4°00 2 eee. scene eee San Francisco.... | A. G. McA. 

409° 2020.8 ns yee Mt. Hamilton .... | W. W.C. 
1 OO SEP a reeneer eee Oakland Jen. CB, 
+ Apr.30,8. mo 1 4b. eee Do, 2 seule Mile Rocks....... Slight. 
We Pe ofen Ss Sl Dn ats eile tere Goi. a ae eee 
1 ya ae ee San Francisco . A. G. McA. 
LD 30. cama See cee ee 73 Fe Peg eg Single swing, A. G. McA. 
2 OY 22a eae eee III | Berkeley......... Northeast-southwest. Short 
and sharp, R. T. C, 
< hD. coisa es seen See San Francisco.... | A. G. McA. 
7 420 2g ta eU on cee ee Oakland...... .... | Shocks from this date to May 
| 17 seem to be of circular mo- 
tion. No decided direction 
shown by Duplex seismo- 
graph. Tremors, vertical mo- 
| tion predominating. Chabot 
Observatory, C. D. 























RECORD OF AFTER-SHOCKS. 419 


Record of after-shocks — Continued. 
































Day. Beginning of | Duration. Intensity, Locality. Remarks. 
Dems 5. secs | 
eprsc0,p: th.) 1, 05.4.0. 2 ioe | ene Mile Rocks. ...... Vertical. Strongest at end. 
LO AEE cea Voici cas. citys Scott’s Valley..... Barely perceptible, F. L. 
Co ia Se eels te ee Cape Mendocino.. | Southwest. Vertical. Direction 
south, very light. 
Wigs Oiteeet ye || esse ke AI eee BUNCK Os. oes o> Slight. 
moemmivasm: | 6 O52: ..5 25 Weer cecs Ia ee Mile Rocks....... Slight. 
SPAN wae eo) Sere eee EIR Cloverdale........ 
May.t, pa. | 9) 19.25.22. PRED) > Py Milena: Healdsburg ...... | Very smart shock, perceptible 
roaring, oscillatory. 
ES ee | ees er, Guerneville. ...... Articles thrown from north to 
_ south. Cracked much plaster. 
OF AS Ghee « eee eae Mile Rocks....... _ Slight. 
Le | ee Cee eee Berkeley ..:...... [ees Gy. 
DRONE RL fall mises ly Bink OO ewer cess | Faculty Club, G. K. G. 
ORO Se oe er aale Leu. ence Ul Opera tac. 3 East-west. Several max. Had 
watch outin 3s., slight shak- 
ing 30 s. more, S. A 
Salt Prat | =s+---- | --.-- | Napa............. | No time given. Three light 
| shocks during day, W. H. M. 
So | eee eho ee Peachland........ | No time given. 
Maye vant) 12 $6.) . ses hs PRS ct tad INE Nas tee tooo Sharp, W. H. M. 
Cis ae one, ON a (ee Los Gatos........ ee ae Sy: 
eS UE et rl a a San Francisco .... | Very light, A. G. McA. 
ss bes ea |e ae II Oskland)<< ie. 2. 2 Chabot Observatory. 
SeoOOPemerawae le fool. Wee pe San Francisco .... | Very light, A. G. McA. 
Mew, poite 4250 1B)sen | 5.4... maf Il Mt. Hamilton... .. (OAROE ae. 
BOD a Sema Vi iak nan. | wes | Banta Crug j...... Lively shake. 
Se2e Sey wien AeA | mets Calistoga ......... 
Cel EA | eee ee S. F. Peninsula... 
LO Gowrewee) | ccs. re Scott’s Valley..... Two vibrations apparently 
| | from SEZ, FP. 1: 
Dd eee | | | Laurel............ | No time given. 
CS velar (re Glenwood ........ | 12 quakes, each preceded by 
sounds. 
igo Ge ty ae ae DEtsi 5-22 ul) ee Scott’s Valley .... | Reported as 6 a.m. in Santa 
| Cruz. Strong vibrations 
east-west. Sleepers gener- 
ally awakened, F. L. 
Oe MR ee ty CS ik Santa Cruz.....-:. 
GOPer a eee cae eee Point: Pinoss. 2. =: Short. 
ORS eee. ce hos: Gatos. 228455. Vertical, I. H.S. 
Gas ra a aa oth, eee San Francisco .... | Very light, A. G. MeA, 
ay hs Be eed a ce Pore © > Oakland :3522222: Chabot Observatory. 
OF a ae ese ees eet San Francisco .... | Very light, A. G. McA. 
Pama bee Tete Sg eT law ay Toe Gatos ee: fey... lye Ss: 
ES ak Es Dea I 2 le i a Scott’s Valley .... | ‘‘ Wakened me,” F. L. 
LFF oe hoses i baal URE Oe el ee Riyal a Point Pinos....... 
Ses a Bee aae II Mt. Hamilton..... Two distinct principal shocks, 
0.5 s. apart, 3 s. after be- 
ginning. North to south. 
No sound. No vertical mo- 
tion, J. D. M. 
ra tel ale ds os ||| ae ee (eet Los Gatoa...-.... ees ees 
fe ny ee . | San Francisco .... | Very light, A. G. McA. 
Osea DE ieor ts he arse | Scott’s Valley.... |Two people at least were 
awakened. Three shocks al- 
most continuous, not severe. 
S$ 30.-2. eae Derr ores ili ser CG ee tees se Very slight trembling for 
perhaps 5s., F. L. 
LOE29 FSO meemenn eae i terol cane os. San Francisco .... | Sharp jar, A. G. McA. 
LOMA OAS Ae obll se elereciee | cists LiGa Gatos 23 24.52 66 IL Ale ish 
ee a er he ee eee ee Campbells... .:../. .. No time given. 
ae 








420 


REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


Record of after-shocks — Continued. 














Day. pemoning of | Duration. |Intensity. Locality. pers 
I Sh. nh 8 secs = 
May 5; a7 my elO.15. eye Sigeas | ete Mile Rocks... 2227- Moderate. 

10 F280 ee eee Oakland epens ee Chabot Observatory. 

1029730 See ee sae ene San Francisco .... | A. G. McA. 

Os | ge enn Ee Berkeley 25. <.s2 Northwest-southeast. Single 
displacement to northwest, 
with return to southeast, 

| B: LN, 

10 29 45 3-2 4 bees II COA ae ee J. N. Le, 

We Oats 0 iis Sette cil ASE IV S. F. Peninsula. . 

10°30 et See ai oes ae Napaswi.g-eee ee Wet, Bie 

10° SOLUS eee Oakland s-s.9- Alameda Pier. 

10 30 05. Ls yom eee Mt. Hamilton... .. We WC: 

May 5, p.m. 4°11 45.2 eee Lites ish Ree Mile Rocke... 2..%. Slight. 
. | NE ne. ees eee Campbell...3.2:-<- 
May? past. |) ye seaeeeern |) teres eal aero San Francisco .... | Several tremors during early 
morning. 
| 205. Jester eee Ios. Gatos ..js¢ . Rotary motion north-south. 
ete ok Meee de aK. Uae Vertical, I. H.S. 
| "Veo. Bee UNL ews ee San Francisco.... | Light, A.G. McA. 

Pe, ek * Ls 2 eee Mile Rocks....... Slight. 

S 59 20 ocean. wea Wee San Francisco .... | Strong. Last one double wave. 
Felt like apush. Then more 
waves, A. G. McA. 

May 6, p.my Sexe eaegaat ie esc eeee Bartlett Springs. - 
| 8 10 eee 10oaee VII |. Upper Lake...... Very violent, almost due east, 
sudden. 

8 12 34.. wo teoae LLE<T Vs)! Wikiah 26e.: 2224: _ Direction west-east, increasing 
intensity. Nomax. Nonoise. 

Watch compared immedi- 
ately ; times probably notin 
error more than 2s., 8. D. T. 

See Ce ve cosmos all Oe oe i cools cee | 

Sr Diek Sere, Miers ote eee G0. Soe 

OP cece eee Btupe VII | Upper Lake...... Me Be eel ge clocks stopt, 

| Bas. 
| 9 -|-". See beeen alee Los Gatos renee | 
ln O'45 Rees 1:22. aimee oe Mile Rocks.....-- 
Luly Lo eee Aetna ane CO.22m ckiriete 
LiL “DO Sen cece eee hos Gatoserase. 2" Rotary, I. H.S. 
Nee. fie eee | Wa epee |) Get Blocksburg 2.25. - No time given. 
| May 7; 8.13}. 2 Goce Seee ae ee een eee San Francisco .... | Several tremors during night. 
| Mek sae eae |) ame rsicelll sess 22 Point Pinos #222. About 3 a.m, 
320 eee Le eee Mile Rocks......, 
3: Ab eae eee rae eae eee (3 (0 as Sl 
& O07 thea oe San Francisco .... | Very light, several light trem- 
ors during night and early 
morning, A. G. McA. 
May 7, Dine) 64.10 See ee Tog Gatos. so. ca: Rotary, I. H. S. 
Al? 10.2024 ee eee San Francisco.... | Sharp jar, A. G. McA. 
A, 30 oa ee Pe re ee ol ee Bartlett Springs -. 
May 8, aoa.) 4 Se ee Los Gatos?.-5-2.- TSH e. 
10 16 eee a eee ene ere Yerba Buena..... Light. 
May 8, p.m. 112539> 2 ee el ree eee San Francisco .... | Light, A. G@. McA. 

A] 40.1.2 See 24), a ee Campbell= a= 

11 40. 42S eee ios Gatogs- nee North-south, I. H. 8S. 

11 40. Sse 5h ee eee PointsPimos!- ee Indefinite as to a. m. or p.m. 

1. 42 2S ee ee San Francisco.... | Sharp jar, A. G. McA. 

11 42 02 103eee VIET) PalowAltowece = No max. No noise. Also felt by 
Prof. L. M. Hoskins, but no 
time taken. Watch com- 
pared with standard clock at 
Ukiah at 10 p.m., May8,and 
at 11 a.m., May 9. 8. Di; 

ee Ae: Townley. 





























RECORD OF AFTER-SHOCKS. 


Record of after-shocks — Continued. 


























Day. B tears of | Duration. |Intensity. Locality. Remarks. 
| 
hee. 8 secs 
May 8, p.m. Sons DRT, | een Pia Salingast se. ee. No time given. 
NMavao a caiieyom2 Gs. Sat tll) = oo ..0:c pile eee San Francisco .... | Light, A. G. McA. 
pe Ee a eee or eal (mma PalovAlian. octane Just one jolt. Not felt by Prof. 
Hoskins; absolutely certain 
it was quake, S. D. T. 

BIBRA Os gee ee ae nike} ONES Danatogaeeie-cs-5-: About 2 p.m. Like explosion 
under foot. 

QAO HAMAS SEPP on as Ve eas eae ae bnurre Kage a «see South-north. Several seconds. 
Shook windows. 

Oa00 - eeces Bo wari Uae Hemndalegass acs J; A.B. 

LOO aererereeh stereo sa2- lI) arcane SALINAS saeee ~ se 
POM SeOHP soe occu. seae LosiGatos~. .... .. | Two light shocks, I. H. 8. 

EA Val Aas ie LD bec eree cin Mes cjalecy.:|) a atas-eee San Francisco .... | Light, A. G. McA. 

GA pase ell |S <n m.0,000 |e sate Blocksburg.......- 

Gaerne a | pee nes Merndalesee.... 5. Ap tosh: 

CxS Osa: Zhe WP ed VPP Hurekaaeteres 25. Slight sudden jolt. South to 
north. 

Te or oe es ee ) Bloeksburg. -...-- | One light shock. 
eR s3. 2 38 yileeet Los Gatos........ | One light shock, I. H.S. 
ao Oat ol Ce Nee Laurel............ | No time given. 

Dee (Be neal eee Montague ........ | No time given. 

Mays tas), 10.sy: fen Ve ane S Mile Rocks....... Slight. 

WO AG ees Nee ce excimer Oaklands. s08- =~ Chabot Observatory. 

1 27 50 PAs escolar Bolinssaeccs- nose 

1 eee WE 2 oe weal) pase = WORDAG aa cawes wate, W.H.M. 

ESO esc Davee dl f4es es Bonita Point ..... Nearly vertical. Prop. NW. 
No tremor, justa jar. 1 max., 
strongest at beginning. 
Rumbling coincident with 
shake. May have _ been 

| blasting. 

1 30 49 Fe See ee ee San Francisco.... | Heavy, A. G. McA. 

On Sy oer Salings so. 5 <<. 

TeAOMAR TOR 3.2 2 Tied) Berkeley o:.22-.55..< Residence 1820 Walnut St. 

TRAD eee ete IM arnere 3% alba nce Kentheld’.2- --...- 

te eo) | oe yee 4 Ios. Gatos.s2.<5-.. Onelightshock. Notime given, 
me By? 

BeaULesaa el. 4 enix. pasate RD Bioeadigsis occsiac.c Wats i: 

Mayu 2-aame 4 OO Sens rei 2. w.- [oteeee OS eae: North-south. 

may la.piiepe i O0c. seve. | 2... <- ‘Sats Gia eis ele nee North-south. 

Marie HI. | BOLO es sist dP ae ceo V S. F. Peninsula... | Caused ground to tremble dis- 
tinectly, and brought down 
broken plaster. 

De apres oe Ns dee... 1) aver San Francisco .... | Sharp jar, A. G. McA, 

ree ee NS ooh | ie ne Campbellizas5.--.- 

2 in eee ete all eee eee fiero os, Gatose sae North-south, I. H. 5. 

OOS ea in), 325 aeesete San Francisco .... | Light, A. G. McA. 

OSs Adib, |) Be sO. cree de 1h 2a. a os oa chan Berkeley. 5. .::... Gra Ge 

A Oi tl) 5. sea biaraeay oe Oe eae = tes GK. G 

Ja Td SS atl le eae ee (i ee PomtePinosie..s-- Vertical. 

OZ eeeeaseewl es oo aig tana Mile Rocks......- Moderate. 

Se ke | ee | Pee Lom ijatas. 3.0.2. WAS: ets, 
11 56 47 ie bias | II-III |} Mt. Hamilton... -- Ending with jolt, Mrs. R. G. A. 

May 15. pom. 4020s. Bo oo. a | at Pee: Gatos. ..<.;... BSS, ay 

OSES OSE eee | ..«.- | Campbell......... | No time given. 

May 16, a.m. | 6 20 cs. Bees | aati: Ferndale .......-. jenn. 

Ma yuLG=pom ah lle, ee eee es ater ya ene Hiebersepe eee 

pW Ws a i eee | 9835 Berkeley < .- s+ Ge KG: 
SP se At BAe te eee Salinas... se...--) | No time given: 




















REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


Record of after-shocks — Continued. 








Day. 


May 17,a.m. 


May 17,p.m. 


May 18,a.m. 


May 18,p.m. | 


May 19,a.m. 








Beginning of 























Backs Duration. |Intensity. Locality, Remarks, 
ja Geol ah secs 

During night | ....... Jmperialy/- 22. Two slight shocks. 

1221842. eke ee ee VI S. F. Peninsula... | One of the severest since the 
first shock, woke all sleepers, 
swayed houses, set dogs 
barking. 

12-730. Se sage d ee Be eee Berkeley ......... GK. G. 

12. Boece eee ee eee T208 Gatos. 3 soe MARL sh, 

11 05.4620) <3 ee eee San Francisco .... | Light, A. G. McA. 

3 40. een Ferndale s...0¢..- s Two more before6a.m.,J.A.8. 

8 15.25.2924 WSR cee eee Mile Rocks....... | Vertical. Strongest in middle. 

Sie ee le Oakland! 6 a0. 5. Alameda, Pier. 

Bile a eee betes V Los Gatos. i235 Short, but with considerable 
vertical motion, I. H.S. 

8720 Fee. eae CeCe ee Balinad o.oo 

8°20 Fecesee 2 es. bee Bonita Point’... ... Nearly vertical. Direction N., 
no tremor, just ajar, 1 max., 
strongest at beginning. No 
sound, may have _ been 
blasting. 

St2Q0iraeeee 22 ud ee PointsPinosseseee Horizontal. Two max. alike, 
sound like waterin pipe with 
air in it. 

$3 2023.5-05 ne ee eee Oakland. 5e-Geee Chabot Observatory. 

Si2li ee PAVE es 2 VI 5. F. Peninsula... | About the heaviest since first 

shock, causing people to 
rush out-of-doors. 

8.21. Aeeeh Gy. once eheene NSD ELL, Cotes heen oe H.M. 

BS Bl peel. Soceads Tee Gonzales ......... 7 

Susi GAs he ooh “ebcc cen cee Campbell......... Violent. 

8 21 17. Lae TV—V" | Onikiand geen Chandelier swung with period 
of 1.25 s. Shock NW.-SE. 
at Vernon St., R. T. C. 

8 21 22. 1B scce¥ IV Mt. Hamilton..... Vertical slightly, 2max.5s.and 
10 s. after beginning, mean 
of two observers, W. W. C. 

8 21 34.. Sal eee one Berkeley ......... . East-west, A. O. L. 

8 21 40.. Qc iil Holingsssce ose 8. A. 

S22 ed Rakes ah Sees Yerba Buena..... Light. 

ey eee yes et) eee | Le eae Berkeley 2. 2m Faculty Club, G. K. G. 

8 DEBS SAIM. Cee eee San Francisco .... | Moderate rolling motion, A. G. 

CONeee Renee McA. 

S 2h Gas eee tooth ee ee eke Cnidale seve, Very slight. No time given. 

of Ol aea ae oe parte, Mat es Si Southampton Shoal | Southeast-northwest. Rum- 
bling before shake and con- 
tinuing 2 s. after. 

«siti MARR OMI ES Oe oo ee ea Livermore........ No time given. 

ee a Smee en han Oe San Luis Obispo.. | No time given. 

12 22 3 2gp ee Berkeley. v.tse: GEG 

1 45. c-q99e ee ee GO.) Soe as Lo ee Ee 6 

Ey crepe ee Los Gatos........ ae Jebase 

5 23%-c tee a) Seat ee wu San Francisco .... | Light, A. G. McA. 

i 56) seed Wee ae el Ls Siktos ete TPES: 

8.30... oe Diner eal eee Cape Mendocino.. | Southwest. Vertical. Direction 
8S. Very light. 

8 53 37. Bagece TILT Wiikialt oye eeee No max. No sound. Watch 
compared immediately and 
clock correction determined 
within an hour, 8. D. T. 

8:56 3 «mee y RN Ferndale, 353.5 -. J.A.S. 

8 555 faa e le eek. Bee Fort Bragg....... 

D 30 i. 5 ae. eae ee ee Blocksburg. ..... 

10 53s. 20-2 oe eee Los Gatos........ LEAS: 

Between 1223) 2, sa eee CG aha ecw Slight. 

2 30. . Se Ae oo es Campbell......... 

2-30 hee eee eee los Gatos. oars East-west. Vertical, I. H. 8, 





RECORD OF AFTER-SHOCKS. 


425 





Record of after-shocks — Continued. 






































Day. din ee ig of Duration. Intensity. Locality. Remarks, 
| aie oc) secs 
LORE 1 G-Star II-III | Mt. Hamilton..... EKast-west, W. W. C. 
Br OU see ae ee a cen frases OOSyoe oa oe 
eA Tent ee hae, Suita ce Pl wees Merudale es 350 Very slight shock, J. A. 8. 
LEGO Se cee cit en sete Tans Gos -Gatoe.... ..s« tse: 
PRY LS, PY SSO on nae & pees <'eerk | fatvare Shel eee 
(WO Taek! te eee Ne Fort Bragg....... | 
Te eegeren fal ee td are ee Blocksburg....... | No time given. 
Diary 20 SACO OS peaes a sles sae 3S bo sas = Carson City ...... Light. West-east, C. W. F. 
Macau, pital 8 Osecdess | we- aces Wise ose Kort Brages. - 22: 
Te COR Serre os 8 Ls 4il| Pade bos Gatos...2i... #1. H..8:; 
Mao aaa oO OU eta c= 6 Sic ted lea nee Mile Rocks...-..- Moderate. 
Nay 21; Dae ROO see en) ce ous (| + tee Los Gatos........ fH. .s. 
ZS OO eerie ase IIL S. F. Peninsula... 
eM eee ee ces | eee ts Dic eebeace dae | 
Binge ete te eee ice | enceeee | 48s 2 losGatosiaa.—- <= | No time given, I. H.S. 
ees oe A aka Ferndale ......... | Before daylight. Very slight, 
JA. 8: 

ERY cote AIL, WE TOU Sola niece | vc wot’ | Mose t= | Bartlett Springs.. | ‘The tremor might have been 
due to thunder.” 

Mawes Sea neee s, 61 asm see P55 Los Gatos. .....<. lho: Oe. £ 

Davos aan.) i o0 2-225 | -s4<-m2 | ==> ee CO Aes oe «esata Lee 

Mayesnin.) 1°28 2.0.22. | -asces5 | +--+ CS a eee I, He Ss 

ad, SS Ee a ee its eee eee Te. 
LINTT 2. ce 2 ee eee Bonita Point... ... Nearly vertical. Direction NE. 
| No tremor, just a jar. 
1 max. strongest at begin- 
ning. Sound like clap of 
thunder 2s. before. May have 
been blasting. 

May 25, 8.1.) 12.582... -«- 45-50) | «<0 Berkeley ......... At Faculty Club. Firstirregular, 
then rhythmie and slow, then 
morerapid. During rhythmic 
part was able to recognize a 
distinctly east-west direction, 
and thought this changed 
later to north-south, but not 
quite sure, G. K. G. 

Mayes, p70.) 10°210 2... GOA coil Cases Wieswate Sosa Began with confused irregular 
motion, but middle and 
final portions definitely 
rhythmic. I tried without 
use of watch to estimate 
period of rhythm, and think 
it was between 2 and 3 beats 
of the second, G. K. G. 

May2r.a..) @arive ose) aoe | eee ss os Gatos: oo I. H.8. 

Ore ell, Aaraevccsie ||P ere os Santa Cruz....-..- Slight shock. 

May 28,2. (9 1200s eee fone ate | weses Lge (78008 a 5 a Ls Ewes 

ea cae 2) i ee Meio Gtk seed ears | ees Ga 
PM Wak 7 Sar tal aed Me a CO's, 5 sais 3: EER F 

May2S,pm-) 10 45ecers-! |<. cece | ee ees Santa Cruz....... 

May 30,p.m./12 37 207... | ...--.- | =-2-- San Francisco.... | Light, A. G. McA. 

May 31,am.| Early....-. | ------- | --+-- MOskGStOSa.4 5.42 = Tans: 














424 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


Record of after-shocks — Continued. 
































Day. Bonesin’ of | Duration. | Intensity. Locality. Remarks. 
fais Tacky Fe secs 
May 31,a.mol).' 5° 45% vecre en eee 5 meee Napa.22e6 teens: Wr Hee 
5 4008427 2 ee eee Berkeley:. .222.55. R. T. C. in bed. Short and 
sharp. 
B 1B ten ee eis et ol ee San Francisco.... | Light, A.G. McA. 
6. OP a ee eee Peach anclemeseres 
June.3, a.m. |) (S'25 eee. -a | o- te ee eee hos*Gatossee oes Lanes: 
0: Ad eSuveet WN ee ell eee GOinn Sane = 
June 4, p.m. | 9:40 5.2.0 eee one eee Ferndale ® 2..tacns Very slight, J. A.S. 
| D1 GA0 see oe 2 Sa ee Mile Rocks.....-.. 
LT BO 2. cwss ll ee eee eee Los Gatos......2. Rotary, I. H.S. 
LL 50 Seales oe el eee Campbell. ........ Sharp. 
|. 11-30-50). aE HI Oakland: ().0 2-0-2 Chabot Observatory. South- 
west to northeast. 
11 Ole oe eee siten /} Mills Golleretet.. 
11 51 07.2.. 604.2. |) IV-=V oS) Berkeley. 2 Ewing seismograph. 
11 51 45 Seo eee eee ee | Chere ae Senate Al Orin 
li 52.675. ee eee | San Francisco.... | A.G. McA. 
£27 AGS S.s a eee eee | eee Napac ees eee No time given. 
11 bbe. See ll Evi ot | eee INELOG ty eiccis aca k 
June-5,/a.m. | 9 00, Seeee een ee. See ae eee Toe Gatos oars. |e 
June 5; pins Wel Lea bee eel ees ore en ee eee Niles 2: 5 ass 
June 7, 022 BO eee eee el ee Berkeleyere eee A. O. L. 
ee ee een lease Hureka Seen tees No time given. 
ee ee | ey PELE (ks Upper Mattole.... | Heavy. No time given. 
June 7, pt: 4 0 ena Boe eee ae wee Blocksburg....... 
fF: Pee See 2 Lh cee a ee Ferndale ......2c.-2. Slight, J. A. S. 
ce ee eet, ak | a aan ese Hortibrago ce see. 
ASME Sees OG Soca cy deewre tee Burekes est ton South of west to east. Sud- 
den, increasing, then dying. 
Shook buildings. Severest 
since April 18, A. H. B. 
June 8, a.T. i) 15. eee eee eee a |e ROnphiosseeer ease 
DO ncpte eileen Was exci) aoe | Wine aie 22 pipes 
JUNE S.p ni On pares PR ae he 5 | Mile Rocks....... Slight. 
Juné:9. acm.) |SUIG8 5 eee eae eee | eee KorteRoss 32 -eeee 
Tb DO bees Oh kee eee Oineatlareteers 
June 9, p.m.) TedO cae, Geeeee se ieee Mills College...... 
COAL cee ie BS ee eee San Francisco.... | A.G. McA. 
June:10; pmsl) e eee ee ea eee Burekalce a: socene No time given. 
A OO sc Repeal eee emer ae | (eee ios! Gatos sence I ES. 
Gu26.2. 7s eae ball ee eee Perndalesass see. Slight shock, J. A. 8. 
Q.. 41 eee Pee ee alee San Francisco .... 
ee eee ae Hees Napaigs. ccs 4 ey No time given. 
June! 1am 4 30s5bip a0 eee eee Coronel Bay, South | 8.8. Assuan. Sharp shock. 
time America: 2... 
ee re SN ee Napa.d-c.c2-<--.. | Noitime. given: 
June12;p,m,|, 2 + toe ee Los: Gatosmeaas-ce 
June 13,a.m.| 1] 5O2.ca92- 0) epee eee Burekacs. as. so. Very light shock. 
ee were ee Tequisquita Ranch | No time given. 
ee (eck: |) oe Campbelloc. 325 wes No time given. 
11. $1 2532S eee eee Ferndale......... Very light, J. A.S. 
June l4,a.m. | 450 ch ee doses saree. Very light, J. A. S. 
June 14,p.m. 











RECORD OF AFTER-SHOCKS. 


Record of after-shocks — Continued. 








Beginning of 


425 














Day. phank: Duration. | Intensity. Locality. Remarks, 
he mss secs 
OU Ra A MIS ea a | aes (ee ee Lge Gatogus. 2.5% 
LO Omer Nee erie. pr ereete GO meee tee 
LO atin He AQ Sel) jabs 3S | eae Fort Bragg....... 
GBS Seal nee ee sate: mene crate Mt. Hamilton..... E.S 
wae th rein 12 O05 Msck ox l\<« <x ces, sew es fog. Gatos... ..... 
U2 OO Sear ae rere an ae 3 28 ee Oe 
ETD rs oh en NM chia aia | Sales HonoMiAg 0. 4..0 5. ; 
UEC aise cee! et ea eee Mile Rocks....... Moderate. 
OSU RLOOEE ce Mee 2c. Mkcete Berkeley ......... Omori seismograph, east-west. 
Component 79 + 10; north- 
south component 76 + 10. 
Qed 4505e= oe Il Oakiandiee-= ee Chabot Observatory. From 
northeast. 
O40 Oe ele asco Wty ase 6s MUOHOMA.s, £. 25 a 2ki- 
QRAQTO2 ne) || Scie Sats © ig! Berkeley ......... Kast-west 2 shocks, 1 s. apart, 
BeO; Ly, 
4d Re Se Fic RG Ty vy Se San Francisco .... | A. G. McA. 
OSA Sac ee cl esas ossGatos ee. 22. 
OF Aree dene c eee ll <b ods Mills College... ... 
Opt cD: Serer ee Se oe Ni us Berkeley ........ Recrs Gy; 
Datars xine Os Mt valehats pa ent Se Ose CS ee Bare W.S. 
O eA Sie eye aimee. oC omcw li roe a cts Livermore..:.... 
OGD lira see ew es 2k = I Berkeleyese ee. A. Osis 
LOS SO gee eet 7 sed Fees re Mile Rocks...... | Slight. 
10 32 04. LD re ere (Meri ote Berkeley .......- Omori seismograph, east-west 
component. 
Dee es ate CIC hee © eres Omori seismograph, north- 
south component. 
Le es = a rere eee San Francisco.... | A.G. McA. 
Se Ash. |e eee ee Peachland....... No time given. 
<a ERM ae ees Mae ee Napa............. | No time given. Three shocks 
reported, W. H. M. 
Dare a Te OAM ess he eects |. ose Los, Gatos... 5... Ie dalise 
SOP GAnC oo) Se ea oe Peachland........ No time given. 
wimneleay i: ) “EGO Cece. 12s. e es 1. =e fee Herndales. eo... Light, J. A. S. 
Diesen anal Gee atl Wl Sneaks COMee bers. Light, J. A.S. 
PUG ES A os SS Tew ccs reenerr ti aes sl. Fort) Ross .. 5... No time given. 
rtieeO Seats LO eke zee, twas ccaee} \ssess Ferndale .......-. Very light, J. A. 8. 
Ee RG Oy Bardeen (A ee ee ee San Francisco A. G. McA. 
aio, eee |W Ge Altes Kentheld: 22 -- No time given. 
ey [eee ee: le fea Mt. Tamalpais.... | No time given. 
June 22, p.im|) 11.40... ..2. ee Ree eas Mile Rocks...... Slight. 
sla oe LO) Pee Sens II-III | Berkeley ........ Principally vertical. Slight, 
tremors for 5 m. after- 
wards, no rumble, R. T. C. 
PR RS Ee eS ee eee, COME see ees; Omori seismograph, east-west 
component. 
DAE eat ater (3 (OR ase SAP pe Omori seismograph,  north- 
south component. 
June25,a.m.} 9 16..2.... Gates Mie ee Ferndale ........ Light, J. A. S. 
eu, | fa Seas UP Ss Ve biten's INaDaS 62 Ase. No time given. 
sett cate || Aa ae Oe Peachland........ | No time given. 
SLL iy Wd oP 2 |e Bort; Ross 4.2... No time given. 
June 28 ee ee tae ee Peachland....... No time given. 
June 30 ee eter a ee ee Upper Mattole.... | No timegiven. About the one 














hundredth shock since April 
18, W. H. Roscoe. 








REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


Reccrd of after-shocks — Continued. 
































Day Begmume of Duration. |Intensity. Locality, Remarks. 
h, m. 8 secs 
July 1 oe eee Bh See eee eee Mt. Tamalpais.... | No time given. 
July 2 B45 nic MORO aoee see el eee Fort Bragg....... a.m. or p.m. not given. 
July 4,8.) O: Bo eee eee a Los, Gatos... 2.6 Dre: 
580 ere eee ee J Mt. Hamilton .... | East-west, E. A. F. 
§ 45 2. cece odecees eee Campbell ic. 3. 226 
HAS: altcbicie ale oe oe eee eee DAU NAS See se ae aes 
July 4, p.to. |) 16 oe ae ee ee San Francisco.... | A. G. McA. 
Ue Ra ere lh ee scers oP | ees Los Gatos........ Uy s OF 
10 "ADO on eis 2 oe OO REORE NE rise I gg & fie 
July 6,a:m. (10 S22eeeres eee | Ps Mt. Hamilton..... Two light shocks. Three vibra- 
tions, R.G. A. 
July'6,pim. (110.562, 7 cere er ee en eee Balinns 302s wees ee 
10 52 1542) 198... | ..%. ‘Berkeley ‘2222222. Omori seismograph, east-west 
component. (North-south 
dismounted.) 
10 O52. occ 2 Wi isda cece eee Mt. Hamilton..... Light. East to west, R. G. A. 
10.158 See eee eee eee cos) Banosies.aeee 
sai Vald yw heen ok eee eee San Luis Obispo.. | No time given, 
| July 7, a.m. #4, oa ae ee Poa nh ee Berkeley ......... Uninterrupted trembling until 
: 6 a.m., KR. TC. and HUF OR: 
July 9, panep a0 0G ose rece eee HUTeKAc le esas eae 
LE SO0 eon ae Sac cet atone Loe Gatos hea: nos Rotary. Vertical, I. H.S. 
LL Os etenveeey es ve exe WGUreK Sa: so owas as 
11740 ree ee eae I eee Ferndale ss. a.scn Very light, J. A. S. 
| July 12; 8.02.) 8s eee eee eseec ens leo eee. Mt. Tamalpais.... | No time given. 
DDB bas cusoe thie Bee aL ea San Francisco.... | A.G. McA. 
| July 13,a.25). 5 20 ee eee eee eee Sierra Madre ..... Moderate, U. S. W. B. 
LOO ieee ae ae ee ee | Los Angeles ...... 
REST SM Ne ciruilis Cbwchreeee Mince ees. Newhall 22 asse-ee 
July 16/6.m.) 19980 eee ee | Los Gatos.......- Northwest-southeast, I. H. S. 
July-17, p.m.) Goieee eee Seo IV Palo Alia. s:t6-6 About 3 p.m. 
July 188.4 “SY 10 eee es ee oe 10s Gatoatinceeacte LE gia betes 
July 18,p.m.| 6°27)a5 0 eee San Francisco.... | A. G. McA. 
July 20;a,m,|" 1/00... 2288 ry ree A Mile Rocks....... Slight. 
1 19 36 35.3 EE Berkeleys2ccc ers: Omori seismograph, north- 
south component. 
Roepe essen || oan Ore eee Omori seismograph, east-west 
component. 
1°19 °42 Say eae Ill Obicsem se mase Sudden jerk apparently from 
east-west with tremor last- 
ing 3to4s. Awakened from 
sound sleep, A. O. L. 
1 20 +e eee eee GO. use ome Sharp shock. Dr. J. E. M. 
+. a2 uot ewe pot lage eel ae Mt. Tamalpais.... | No time given. 
1230'S. See Ce eed San Francisco.... | A. G. McA. 
July 21, p.m.) 10.10 foe | Los Gatos... aes: North-south. Vertical, I, H.S. 
eiklee fo hone een ae San Luis Obispo.. | No time given. 
July22/a,m0.|° 0015) 0) te) 85 mi.N.86° W. from | Slight shock reported by Capt. 
Cape Mendocino J. R. Sarrins of schooner 
Espada in Lat. N. 40° 
33’, Long. W. 126° 15’. 





RECORD OF AFTER-SHOCKS, 


Record of after-shocks — Continued, 


427 





Day. 


Beginning of 
shock, 


Duration. 


Intensity. 


Loeality. 


Remarks, 














July 22, a.m. 


July 22, p.m 


July 23,a m. 


July 23, p.m 


July 24, pm. 
July 25, p.m. 
July 26, a.m. 


July 26, p.m. 


July 27, p.m. 
July 28, a.m. 


July 29, a.m. 
July 30, a.m. 


Aug. 1, a.m. 


Aug. 2, a.m. 


Aug. 3, p.m. 


Aug. 4, a.m. 





aD AO 
—" 
oO 


(LOMO Ses 
Between 
8 and 12... 








eee cr eee 











ct eee 





85 mi.N.86° W.from 
Cape Mendocino 


do 


Dall JOSeh soee ose 
os Gatos sees ee 
Mt. Tamalpais. ... 


Imperial 


San Jose 


Berkeley ......... 
do. (Same 
record.) 
Mills College...... 


Pernt Womarensees 


Mt. Tamalpais. ... 
Berkeley <2... 2) 2. 


San Luis Obispo. . 


OrtOELORB enone 
Plantation 


Plantation 


Mt. Hamilton .... 


Lat. N. 40° 33’, Long. W. 
126° 15’. 


Horizontal, H. F. R. 
Horizontaland vertical motion, 
R. 


H. F. R. 
lin dala Sy 
No time given. 
es 2 


ls: 


EB: Rs 
H.R. 


Omori seismograph, east-west 
component. 

Omori seismograph, 
south component. 


north- 


on 
a oa 
Po po my 


No time given. 


1 Ea a8 


Hy Bo ke 
No time given. 


Light. 

Very light, J. A. 8. 
Vibration from southwest. 
No time given. 


G. We G 

Hard. Rumbling noise from 
ocean for 2 days. 

Slight. 

Omori seismograph. 

Duration, east-west component 
2m. 484 10s. 

Duration, north-south compo- 
nent 1m. 36+ 10s. 


Heavy,followedbyslightshock. 

|G. W.C. 

Lat. N. 25° 35’, Long. 110° 06’ 
W. Ship Alex Gibson. Very 
heavy shock, 

Lighter shock. 


Two more shocks, very light. 


Heavy. 






































428 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
Record of after-shocks — Continued. 
Day Beginning of Duration. |Intensity. Locality. Remarks. 
bia tis. secs 
Auge: 4; pim AA Te 2. oe Sa eee Il Berkeley. << .% vee Faculty Club, slight vibrations, 
Hons. 
Aug.5) 8.00. |) Ogee eee ea, eo ee Fort Ross... ... 5 G. W:.& ; 
ty Dont eS aemticgs Il Berkeley’... 2...5~ Faculty Club, slight vibrations, 
ta Ries 
3 D6 ee ee eee if Gta cates Faculty Club, slight vibrations, 
Hy Re 
691 5%.4ee apes ee ull LOR ars fete tore Faculty Club, slight vibrations, 
Hy PR, 
Augs 65am 1053292. arene eee rere II Mt. Hamilton .... 
Aug. 8, p.m. | .6 .66-5(m 2 [i--- 32 ee Los Gatos... 24 <2 lh. 2s 
ce bs Pere. Ree cra ills cleres dOige bem Veber 
Aug.12;a.m2| 6 00 22. dk. ieee eee eee Rio: Vista. stages 
Aug: 14, a.me|\"S8 230 See oe ee eee SSUINEA. 2: ee oes Light. 
9 35 SORE RR. Bea ie es COM 4s, Light. 
Aug. 15.a.m,} 2,07 G5.0-2 | faces rere re Berkeley..22--.<< Omori seismograph in east- 
west component. 
4 AQ Sefe ORO ee leer Tequisquita Rancho 
Aug. 16, p.m.) 4 AT 7b Se) coe one ee ee Berkeley. joscae0 Omori seismograph. Duration 
1240 
7 45 ship's 493: mc. 7) See Coronel Bay, S. | SS. Rameses. 
time America........ 
Aug. 19, a.m. | 1: 50:2 Ste vee se ce cee Salinad-2 0 Ss s45 Sharp. 
ye Ts ty) ee See ae Tequisquita Rancho) Tremor and jolt, A. G. McA. 
9 eseaee . o. WE Ease alli Pecereee San Francisco .... 
Aug,21,p.m.) 12 1572s oe t mye. | poate Lat. N. 26° 19’... | Gulf of California. Heavy. 
Long. 110° 25’.... Bark St. James. 
Aug.22, a.m) 1°55, as2ec20) aon ae eee Napa, eivnstiee’s = i Wes. Me 
Aug. 25, p:im;| 1 40a eee eee Ferndale’. oo... Light shock, J. A. 8. 
Aug. 26,p.m.| 9002 e202. en ea OO ae ee Light shock, J. A. 8. 
Aug. 27;a2m.,| 10:.0....<) nae ee cere Point Loma...... 
Aug, 28 8:10 3 |_: Beye een erro ene Herndale 2 -s.. 2 Ja ASS: 
11. AQ. Gey 2 ee eee Tequisquita Rancho 
Aug.29,a,.m.| 7 59 35...- D tas ae Mt. Tamalpais ... | Southeast-northwest, W. W. 
Thomas. 
Aug. 30, 2.14) 0g2 012.45 52a SOMOM dees eee eee 
Aug. 31,a.m ind) AZ dencese il ee eel Glin S85 eee 
9 82. race es eee Fort: Rose. 2252-5. 
Sept..1, acm, 43512 seen tee eee SONOMA, 25 aciacke oe Light shock. 
5 DO et) eels ee eee Tequisquita Rancho 
Sept.(2; a.m. 68 Abe oe 1 ss eee Lat. N. 43° 40’... | Bark Agate. Heavy. 100 miles 
Long. W. 128° 50’ west of Coos Bay. 
3.55.22. & aati ccahee eee Lat. N. 43° 40’... | Not so severe. 
Long. W. 128° 50’ 
Sept. 6,41, | 120104. eee oso Branscomb....... A. J. Haun. 
Septes, am... 6:87 one 5-102) see San Francisco.... | Very faint, G. K. G. 
9 24 59 10 ves2 II-III | Mt. Hamilton .... | Perceptible vibration. One 
slight shock. East to west. 
D 80 Foie .c22)| certers Seen) eee Santa Cruz 











RECORD OF AFTER-SHOCKS, 


Record of after-shocks — Continued. 


429 





Beginning of 





Day. eicek. Duration. |Intensity, Locality. Remarks. 
Hynes secs. 

Sepe.o,pm.} 12'32....... 20230 eee: Berkeley ......... Faculty Club. To and fro mo- 
tion with period of about 
0.5s., but closed with ir- 
regular fluttering motion, 
G. K. G. 

Bembadatn my 400 ee Le ee: Wh ee Grass Valley ..... Southeast-northwest, J. Sanks. 

Ee te) | Oe ee ae ier an Carson City....... C. W. F. 
AS OO eee a oe ee eM Pilot Creek. o5_ 4. E. W. Stanton. 
Piawecie nas Nl cake. ee lt! pees Nevada City..... S. W. Marsh. 
eee eee ec oe al, Wabuska, Nev.... | Tremor, J. G. Young. 
‘co URE Ma Be ak gatos ye ee ean Lat. N. 43° 02’... | Bark Palmyra, 48 miles W. of 
Long. W. 125° 41’ Cape Orford. 

SUS Oe EE a er irr Ferndale: ... <<<. Short, J. A.S. 

Sept.14,a.m.| 8 46....... Be Ge. tae a a Berkeley ......... Omori seismograph, east-west 
component (origin probably 
435 mi. distant). 

ae eat 202-2. | =.->.| Lat, N. 41° 78’... | 85 mi, NW. Cape Mendocino. 
Long. W. 125° 52’ (No time.) Schooner Robert 
Searle, 
he Lee | Min a ee 18 Cs Mt. Hamilton.... | Several observers give north to 
south, Duplex showed E. 
20° 8S. 
Sere. iy, p.tt.) “6.1500. Lt Bey Ferndale ......... J. A.8. 
eta ed PY ee seare tN seicon. 2 (0 te, Si eee J.A.8. 

Rh eee of ae ee J. AS. 

pereccurprin| 2°20 2,..9.. | 2... Mare Island...... From 20° W. of 8. movem’t 3 s. 
elo eae en ie Berkeley ......... | Faculty Club. Slight, G. K. G. 

SCA oe WR a HOE sah eee Faculty Club. Slight, G. K.G. 

Pert so, er Or eO gs te ek |. 55 o52 26 (aR, See Faculty Club, Slight, G. K.G. 

2 Rl ok ene ee, i Mare Island...... From 5° W. of S. movement 

: $s. (No time.) 

Beet OST ie 00 couse eae ee | es San Francisco .... 

Ot) Oey eee eee eee Hort: Ross... Cen Wig Oe 

EEO CAG So roe shel wenn c, Py was des Tequisquita Rancho 

“US oS PUES Bt ae ES ae ee ey San Francisco .... 

Pei hi amis Boh SO bl to, palinag. oo. 

TUL sa eg A. | oa | Berkeley ......... Omori seismograph. 

See Li) Ga eee ate earth kn cee. Peet Fort. Ross ........ During night, G. W. C. 

eho Aa Ae ee eee fs, oats | se Tequisquita Rancho 

cate Wal sae ie, po. .cc ks occ ed Berkey. sc. Omori seismograph. 

Nova wan, itt hehe aes de et ts | See Reet Hops: ache 

OVE Ons we hee Boe ea Zao Ae cable een: Lat. N. 46° 09’... | No time given. 

Long. W. 125° 22’ | Sharp, followed by 3 moun- 
tainous waves 55 mi. W. 
of Cape Disappointment. 
Schooner Stanley, 
Ov, ek ee eee eo No time given. 

















Poreka eet eee 























8.8. 


One 


430 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
Record of after-shocks — Continued. 
Day. Bene of Duration, |Intensity. Locality. Remarks. 

hen es secs 

Nov: 9)e.00. |e? 2 bee soe Mee tes ater eee Fort Bragg....... 

Nov.118.1.| 6 40. ship ea) 2224-4) aeeee Lat. N. 42° 51’... | Ship received a quick rolling 

time Long. W. 127° 51’ motion, and a few seconds 
after trembled fore and aft. 
Bark Carondelet. 

NOV. 12,8.000) ga cen oe ee ee ee SPITE Seo oe Soece Light. 

Noy ..13, 8.000). ee ee ee eee Hort: Bragge>.. 2... 

7 AY AQ. de Pee See eee Mt. Hamilton.... | One jolt. North to south. 

Novel3,pim.|) 7 48.5 epee eee ea ete Glenwood ........ 

fae ROE meena <n ae hig 3 Tequisquita Rancho 

TAS cee eee ee Be Pe es he dey an) OSG nae ae eee Sharp. East to west. 

Nov:14,a.m.| 2° S023...26 1) es eee Fort: Brage vo.c. a2 

Nov..J4-16 Oh oo tore a tet ol eon Hort os8 xf <see During night. 

Nov. 16,9404) 12, 8040 ocns eee een eee Berkeley... 2 22ee Short tremor, G. K. G. 

Novy.,.22,);00;)) 03. 00ce ee seen tole eee oael eee Glenwood ........ 

10 AD eects hoe ere, | eee Isabella cease oar 

Noy.25,D.10.4 ch 05 eee oes eene ull ere San Francisco.... | Very light. 

Nov..26;8.407| oh aint Sales Glen ee eae a eee COs. wake pate No time given. 

Nov.26,p.m.| 10 27. S<10.24, 22 oy Lat. N. 14° 41’... | Sharp shock. About 20 mi. off 

Long. W. 92° 36’. coast of Guatemala. 
Newport. 

Dec.2,a.m. 19's see ell oa een ||) eee ay SCLC OV ere eee First stronger, G. K. G. 

Do DE ee ey ke eg eee Ota ee Increasing in strength, with 
regular horizontal oscillation 
with period estimated at 
about 0.5s. Became irregu- 
lar toward end, giving sense 
of fluttering, but superposed 
on the irregular motion was a 
regular beat with an esti- 

; mated period of 1 s., G. K. G. 

Dec..6;2.m. Wy" 62 40ers eee eal eee Tequisquita Rancho 

aie Welt ettcem Flite seen eee San Luis Obispo.. | No time. 

Dees7, pan. |10) 85 25... oe eee San Miguel....... 

Dee.8, a.m. (10°40 3222 os eee eee Idyllwild 7s ass0 es 

Dee. Spi, 00s tS eo 4 PAS, <5 ~ | Mt. Tamalpais.... | Light shock. 

Dec:9).a.m: |) 283202... 2ee alee eee Ill San Francisco.... | Duration a few seconds. 
marked wave southwest to 
southeast, A. G. McA. 

3 20.67 2S. tee eh eee Mills College. ..... J. Keep. 

3220Se ee 20 aes aliens ‘Berkeleym esa Southwest-northeast. 

3 20 40. 6.2. Wee eee Oakland ~<-35..7 22 Light, C. B. 

Dec.10, pai) 2 ahGaaeer ee eee Escondido ....... 

3 He iat aki A Geass Brena Cuyamaca........ 

Deo.22,a.1:.| 8145 Gee. dees ees CalexicO meee ee 

Dec, 23,8.m.'|, 4 oot eae a eee eee eee Cuyamaca........ 

EDO os ea cumeeetn CaN Calexieo /<. jae nas 

D BO stent af Mes ae ae ch ete HortsRoss>; 225246 

920 DOs cet cies Berkeley ......... Omori seismograph, east-west 




















component only. 








RECORD OF AFTER-SHOCKS, 


Record of after-shocks — Continued. 


431 








Beginning of 


== 


-= 











Day. iook: Duration. |Intensity. Locality. Remarks, 
h. m s secs 
EE 2a es i eo ear |r at VC) a ee Sharp jar. 
RRO R Os PBben SLB ios. stasiae ill Paros a noe | Sa aw Rohnerville ...... 
OURS ety asis askew eG es Aigrelte. oes 3 
a iat Male ee ed a ee Lytle Creek ...... In the early morning. Light. 
1907. 
Ao RI be SA OOO atte | aac Pa oo Kentfield <<: 32... 
‘Re See eh Op, Re eae | a Santa Cruz....... Regular rocking motion. First 
north-south, F. L. 
PAM POM Dig 60 Gosia | cece. be sons Bert Ross 28.4 6.3% 
CSAC ee ee en a es Balitias. 2. io)... 
USSG a ee eae in ae Payiiwild se... ot 
PUSAN AD Gir: | 8s atc) ce. 
MEO teoceg te sh seco | os one Berkeley -3...22-, Omori seismograph. 
RA sO 5s Sehcie Sn eee eh ge aac G..K. G: 

Santa Cruz....... First shock, then short, ominous 
lull followed by quick,vicious 
shaking and twisting, which 
lasted not more than 4 sg, 
Seemed to come from north- 
west, F. L. 

UM LAL ee ee | ee a a Campbell......... | Sharp. No damage. 
APEUCe eRe le csemsel |. Bye NUEB Ok oe cen x. 
SE ee ea ae | aenes jo EY i eeepc 
Noe ee ee a ae Los Gatos........ tH: Ss: 
RIA eek te ce eelee Woaa. San Francisco .... 
BMecO cama |) ages | ese’ Glenwood ........ 
teseee | seeee-- | «+... | Boulder Creek.... | Hour not given. 
i ae RC ig i ee ee | VI Santa Cruz....... | Sharp jolt, F. L. 
4 31 36. Ni ngs al | »Berkeley ......... Omori seismograph, east-west 
| component only. 
Jan. 9, p.m. | 12 39 42 ROT bee Cs Sa plier aie Omori seismograph, north- 
south component only. 
ORES 4 en en ae Tayewild ose. ox 
MBP SS: 40505). oces, h ccc... |. cue Blocksburg....... 
CET ee ce ley 0 | Oe at Os ar Pere aoc soc sued « Light. 
UA Ean ee Berkeley ......... Omori seismograph, north- 
south component only. Du- 
ration 18 m. 15 s. 
2 7 es ns eee Fovilwild 026.20 
LOGE | GL ee en TSADOUA occa ou sk Light. 
9 36 00. Ate ees Nee tae, - Berkeley 2. 4... 252 Omori seismograph, north- 
south component. 
9 35 45.. Pd Sie al Nar Oe Berkeley......... Omori seismograph, east-west 
component. | 
Jan. 23,a.m.| 10 53....... (ta ee ee OG: gon deen 25s _Omori seismograph, east-west 
and north-south components. 
Jan. 25,a.m.| 9 25 38.. O00 sas3 39> PaaS GOrse55. Sas xi Omori seismograph, north- 
south component only. 
10 39 50. CU rare aaa ee Gorse ses.45s Omori seismograph, north- 
south component only. 
10/56 12.. LSS res aie Soe Berkeley......... Omori seismograph, _north- 

















south component only. _ 





J 




















432 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
Record of after-shocks — Continued. 
Day. Resins of Duration. |Intensity. Locality. Remarks. 
hy om. 8: secs 
Jani 25,p.m |) 3224 1B aay.) eee Berkeley. c.kc Omori seismograph, north- 
south component. 
3 24518ice2 | Sbnsaet (aeeeee Grae ante Omori seismograph, east-west 
component. 
3 BY1S fee Wi een eee doce aan Omori seismograph, east-west 
and north-south components. 
Jan. 26,am.)10 13 47-. PH Reeve) AOS Gossee cee ce Omori seismograph, north- 
south component. 
10 14 08. 10 eel eee Oss >. See Omori seismograph, east-west 
component. 
10 24 49.. BOs sie | amen eee IY rae Omori seismograph, north- 
south component only. 
Jan. 28, p.m.| 2 42 18.. DOAN A on tiee dors vee Omori seismograph, — north- 
south component only. 
ANG 54g ea ee eee a ene QOL ee Omori seismograph, north- 
south component. Slight ir- 
regular shifts. 
AVTS -44 se ME.) orb etree OG vee Omori seismograph, east-west 
component, 
Jan, 29, ia) S00 Bee he Scams, dl terente (ale pees aes: Omori seismograph, north- 
south component. 
5°00 BIA) 2 ese eee GOls cs ee ae Omori seismograph, east-west 
; component. 
Jan, 20; Dan 2. cscs Peak eee eee Kentfield. ........ ; 
Oe 5 Oy eee a See ee Berkeley)... ..c2-. Omori  seismograph. Both 
components. 
Be tase ce |) Soe een eee | San Francisco.... 
Jan.31,:a.m;) 12308 Pee eee een ee ae Kentfield... -23-0 
O67 oe eee ieee ee Mills College...... 
12.30.59, 22. See | eee SOnoms 2.2.5 sae Light. 
12 30 18.. G40 cee al oe Bee Berkeley .......-- |; Omori seismograph, —north- 
_ south component, 
12 30 32.. Lee seen || enctose GOs anes eee ee Omori seismograph, east-west- 
component. 
WAL Ps hy hi tropa MR eee FT| aA ie” Niles faye eee 
WHER Pace Madsen ce sso Abhe San Francisco.... 
12 Sb oes |e ee eee Dan!) JOses see) Sharp. 
12.535 Sicesceally ee eas oe ee Watiices testes oe: = 
12¢36,06222-4) eer Ill Berkeley ......--- Awoke people in my house, 
BR. eG, 
Phen A 2k Ap eee Boulder Creek.... | No hour given. 
Rebs 3) asic el 0 eo0 seer S ieee cee Lat. N. 37° 35'.... | Neither shock was violent, but 
10's: se ete. Bore 4 Long. W. 123° 35! a decided trembling motion 
east-west, 28 geo. mi. S. 
73° W. from SE. Farallon, 
Schooner Melrose. 
Feb. 3, DMs |et co arena ee eee eee Tivermores ee 
Feb. ‘5am! 425 eee | eee ee Las Porte see ae 
Feb.i135a.m.|1 050 see ei een eee Livermore. ...-.-- 
Feb.) 1459.70) 0.240 ores seen ee eee eae eee GONE ween 
Febi16,.a:m vie? 09 [305 ec nee ee eee Point: Gomsaee ans. 
Feb. 25, a.m>| .5 16.4055 Meee cael eee Wurekal eee 






































Beginning of 


RECORD OF AFTER-SHOCKS, 


Record of after-shocks — Continued. 





























433 




















Day. Diaickc: Duration. |Intensity. Locality. Remarks, 
bem. secs. 

Mary ii pam.) 11/58... 225: 20355 ne ee Berkeley ........- Faculty Club. In bed at time, 
3 phases. First more than 
one-half total time, rapid 
tremor. Period averaging 
less than 0.258. Second 
about one-half total time. 
Higher intensity. Motion less 
irregular, period estimated 
at 0.5s. Third, compara- 
tively short. Motion irregu- 
lar. Average period shorter 
than second phase. Intensity 
at first same as second phase, 
but rapidly declined, G. K. G. 

EET ROE SS Te a ee es i ion it a Omori seismograph, _north- 
south component. 

BBOsUOs er We ner see Rest Jossast i. c's Omori seismograph, east-west 
component, 

Mar. 30,p.m.| 2 28 22 ty gh PS res COGS. =5.1365 Omori, north-south component. 

2 28 22.. Te, oe Oi giesipess Omori, east-west component. 

Apr. 14,p.m.| 10 40.0..... DAN Ae ive oe Us tuies soar = Omori, north-south component. 

10 32.2m by fe ee eee a oe ee Omori, east-west component. 
May 12, a.m.| 10 21 31... Jee oem dpiaes aes out Omori, north-south component. 

10 21 ol. i, on ee Di ae caer ih ches Omori, east-west component. 
June 5, a.m. | 12) 26: 37... OSte ies eee GOMsaeeeee Omori, north-south component. 

12 26 37.. "en OS core aie 2 Omori, east-west component. 

12 26 36.. 35.. | IV-V MQ contre aed Observatory, R. T. C. 

NPD Zod eS betes | Sacer ie 2 OVO Wie Aetee chs Eda a Observatory, S. E. 

Junel0,a.m.| 9 47 51.. ec) RM eer OOirebs'.a6'< es Omori, north-south component. 

0 47-510. 23255. fp Grew DOteeeateh- Omori, east-west component. 
eg ee ete hy Tana Hee 8 pee agree ae At Faculty Club, S. E. 
9 48 05.. RO eee Nie cone ch (3 A Se At home. Asleep, A. O. L. 
OAT SOT.3c t! yee! abe Iil dorreeee 235 2011 Bancroft Way, R.T.C. 
iA Be Cee hae ah a fe ee OG ge Aan. stn Omori. (Doubtful shock.) 
ot 
KEY TO INITIALS. 
= W.R. E.= W. R. Eckart W. H. M.= W. H. Martin 
™ ore ar a S. E.=S. Einarson A. G. McA. = A. G, McAdie 
W. B.= William Barry E. A, F.= E. A. Fath B. L. N. = Burt L. Newkirk 
A, H. B.= A. H. Bell C. W. F.=C. W. Friend C: D. P.=C, D. Perrine 
C. B. = Charles Burkhalter G. K, G. =G. K. Gilbert J.G. P.=J. G. Plummer 
K. B. = K. Burns A. M. H. = Adelaide M. Hobe He RR Be Reid 
G. W. C.=G. W. Call J. N. LeC. = J. N. LeConte J.A,S.=J. A. Shaw 
w. W. C. = W. W. Campbell A. O. L.= A. O. Leuschner E. S.= E. Smith 
R. T. C.=R. T. Crawford F. L. = Finette Locke 1 H.S.=Irving H. Snyder 
N. E. = Nelson Eckart J. D. M.= James D. Maddrill Ss. D. T.=S. D. Townley 


2F 


COMPARISON WITH OTHER SEVERE EARTHQUAKES IN THE SAME REGION, 





THE EARTHQUAKE OF 1868. 


The earthquake of October 21, 1868, was most severely felt in the region about San 
Francisco Bay, particularly on the east side in the vicinity of Haywards. The time 
of its occurrence is variously stated from 7° 47" to 7" 54" a.m. It gave rise to disasters 
in the city of San Francisco, and some people recalling the event vividly are of the opinion 
that the shock was as severe as that of April 18, 1906. Early in the investigation of 
the latter earthquake, it became apparent that the relationship of the two earthquakes 
would be an essential part of the inquiry. Shortly after the earthquake of 1868 a com- 
mittee of scientific men undertook the collection of data concerning the effects of the 
shock, but their report was never published nor can any trace of it be found, altho 
some of the members of the committee are still living. It is stated that the report was 
supprest by the authorities, thru the fear that its publication would damage the 
reputation of the city. Our knowledge of that earthquake is therefore not very full, 
and is contained chiefly in the newspaper reports of that day. A summary of this data 
is given in Holden’s Catalogue of Earthquakes,’ and by Griesbach.? 

With the object of supplementing the facts regarding the earthquake of 1868 recorded 
by Holden, for the purpose of comparing it with that of 1906, an inquiry was started 
and intrusted to Mr. A. A. Bullock. ‘This gentleman has reviewed the periodicals of the 
time, and has interviewed many people who experienced the shock. He has also ex- 
amined the region of maximum intensity, and has had, on several of his trips, the guid- 
ance of old residents. In response to a request by the Commission, several people 
have written an account of their experiences at the time of the earthquake of 1868. In 
this way a considerable body of valuable information has been gotten together, which 
supplements to an important degree the extant accounts of that earthquake. 


THE FAULT-TRACE. 


It appears from Mr. Bullock’s inquiries that the earthquake of 1868 was due to an 
earth-movement along the base of the hills which overlook San Francisco Bay on the 
east, and which are often referred to, particularly farther north, as the Berkeley Hills. 
These hills present a remarkably even, straight front, and without doubt represent 
a degraded fault-scarp. Along the base of this scarp a crack opened on the morning 
of October 21, 1868. This crack is regarded as the trace of the fault which caused the 
earthquake. Its position has been determined at intervals along a nearly straight line 
from the vicinity of Mills College, east of Oakland, to the vicinity of Warm Springs near 
the Santa Clara County line; but the evidence of its existence to the northward of San 
Leandro is not very satisfactory. The county was then unsettled, and the information 
consisted of reports of cow-boys riding the range. From San Leandro southeastward, 
however, the evidence is full and conclusive. The general trend of the fault is north- 
west-southeast; or, to be more exact, N. 37° W., a bearing almost the same as that of 


——hs 





: Smithsonian Misc. Coll., vol. xxxvii, 1898. 
? Mitt. d. k. k. Geograph. Gesellsch. in Wien, Band xii, 1869, pp. 223-231. 
434 


PLATE 144 









METAS OS AS Eo Ra Sea SS. . 


A. Flour mill, Haywards. Wrecked by earthquake of 1868, B, Edmonson’s warehouse, Haywards. Wrecked by earthquake of 1868. 





C, Flour mill and warehouse, Haywards. Wrecked by earthquake of 1868, D. Pierce's house, Haywards. Earthquake of 1868, 





E. Haywards. Wreck of buildings by earthquake of 1868. F, Court-house, San Leandro, Wrecked by earthquake of 1868, 


From photographs preserved by Mr. H. Bendel. 





Effects of the earthquake of 1868 in San Francisco, From photographs preserved by Mr. H. Bendel, 





‘ 
i 
| 
t 
' 
{ 
} 
"4 iS 
et 3 
i 
¢ 
Per) oh 


ert pay ame 


- 


es pweetegerees et 


i T= 
Ls Pea } 
at 
. 
ah ‘ 
a 
' 
be 
z 


. 
— » é 
' 
tO) i 
‘ 
f 
# 
i 





COMPARISON WITH OTHER SEVERE EARTHQUAKES IN SAME REGION. 435 


the fault-trace of 1906 along the San Andreas Rift. The position of this fault-trace is 
shown on map 4. While in general it lies along the base of the old degraded scarp, it 
is still, for the most part, within the hill-slopes and not in the alluvium which extends 
from the base of the hills. In some places where it crost the lower ground, the crack 
showed faulting or displacement of 8 or 10 inches, but from the accounts given it is not 
clear in what direction the faulting took place. The statements indicate a slight down- 
throw on the southwest side. In other places a displacement of 3 feet is said to have 
been observed. In places the crack along the fault-trace opened to a very considerable 
depth with a width of 10 or 12 inches, and remained open until filled with falling earth. 
On the higher ground of the hill-slopes no open crack was observed; there was merely 
the trace of the rupture in the sod. This fault-trace could be followed at intervals for 
20 miles southeast from San Leandro, and it had a straight course without regard to 
the contour of the hills. In some places it was quite at the bottom of a hillside, while 
at other places it was high on the slope; and on at least one low hill it past near the 
top thru a saddle-like depression. Springs are common along the base of the hills, 
and the fault-trace was above the springs. According to the testimony of old residents 
the flow was not affected by the earth-movement.' In the hills to the northeast of the 
fault-trace, however, new springs were started and old ones revived, altho some few 
ceased flowing. 

That the crack extended down into the bedrock is testified to by many who observed 
closely. ‘Three men reported that they tried to sound the bottom of the crack, but were 
unable to do so. In the vicinity of Haywards it is reported that there were two branch 
cracks from the main one, trending off into the hills. Water and sand were ejected 
from the crack in one place. 

Between Decoto and Niles the crack left the base of the hill front, and deviating slightly 
from its general trend thus far, crost the plain of the alluvial fan of Alameda Creek at 
the mouth of Niles Canyon to the foot-hills at the town of Irvington. For the greater 
part of this distance, it appeared as an open crack. It past thru a lagoon about : 
0.5 mile in length, following closely the longer axis of the depression, and the water of 
the lagoon was drained out, apparently into the crack. At Irvington the crack became 
coincident with the very straight and even ancient fault-scarp of the foot-hills south- 
east of that town. ‘This ancient scarp has a strike of N. 38° W. Beyond this it was 
not observed farther than Aqua Caliente Creek. 

Immediately to the east of Mission San Jose, entirely within the hills, another crack 
opened with a strike of N. 18° to 20° W., which, converging upon the crack thus far 
traced, extended south as far as the county line. 

The greatest intensity of the earthquake was along the crack and in its vicinity. On 
the projection of this line southward into Santa Clara County, the intensity diminisht 
steadily as far as Morgan Hill, where it again rose. At Gilroy, Hollister, and San Juan, 
according to reports, the intensity was sufficient to throw down a few chimneys and to 
crack some brick and adobe buildings. 

The greatest damage was done at Haywards, where nearly every house was thrown 
off its foundations; while at San Leandro the shock was less severe. (See plate 144.) 
A house near old Blair Park, in the present Piedmont district of Oakland, was badly 
damaged. The only other town of that date in close proximity to the fault-trace was 
Mission San Jose, which lies in the hills a few hundred yards west of it. In this town 
were several adobe buildings, one of which, a church, was wrecked. Many chimneys 
were thrown, but the general effect was much less severe than at Haywards. 





and McCarthy, of San Leandro; Messrs. O. Hill, F. I’. Allen, F. Wrede, and H. V. Monsen of Haywards; 
Mr. Decoto, of Decoto; and Mr, W. Berry, of Niles. 


436 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


In general, the direction of throw of objects was north or south. rom several tanks 
the water slopt north and south. Nearly all the chimneys reported were thrown 
either north or south. Several frame houses were thrown south. One of these, 0.5 
mile south of the line of the fault, was thrown 4 feet and another on the line was violently 
thrown 6 feet. 

Several people report that rumblings preceded the shock, coming apparently from 
the south or southwest. Others saw a wave-like motion set up in the surface of the 
ground approaching from the south or southwest. 


THE EFFECT OF THE EARTHQUAKE IN SAN FRANCISCO. 


At San Francisco and nearby points the earthquake lasted for about 42 seconds. 
It was in general north and south. A second shock followed the first at 9" 23" a. M., 
and lasted for 5 seconds, with the same direction as the first. Until about 12" 15" p. m., 
light shocks continued to be felt about every 30 minutes; and inside of the 24 hours 
immediately following the initial shock, 12 minor shocks were felt. The first indication 
of the approach of the earthquake was a slight rumbling sound, coming apparently 
from the direction of the ocean. The sound was heard very distinctly in the lower part 
of the city, but the residents on the hills do not appear to have heard it. (San Francisco 
Times, Oct. 21.) The shock commenced in the form of slow, horizontal movements. 
The oscillations continued from 10 to 15 seconds, growing more rapid and more violent 
for 6 or 7 seconds, then partially ceasing for 3 or 4 seconds, then increasing in force and 
rapidity for 4 or 5 seconds, then suddenly ceasing. (Alta California, Oct. 22, 1868.) 

There were no abnormal barometrical changes at the time of the earthquake. No 
chronometer in Mr. Tennent’s office was disturbed or showed any change of rate. The 
pendulum clock in his office was not stopt. A transit instrument erected on Russian 
Hill, belonging to him, was not disturbed in the slightest degree. Two magnets, one in 
his office and one in charge of a friend, showed no loss of magnetic power. One was 
loaded to its full extent, and the slightest loss of power would have permitted the weight 
to fall. (Bulletin, Oct. 22, 1868.) 

The portion of the city which suffered most was that part of the business district, 
embracing about 200 acres, built on ‘made ground”; that is, the ground made by 
filling in the cove of Yerba Buena. (See plates 145 and 146.) The bottom of this cove 
was a soft mud varying from 10 to 80 feet in depth, and the material used to fill it was 
largely “dump” refuse, much of which is organic and hence perishable. Many of the 
buildings of that period were built flat on this filled mud, without piling, and before 
the land had had time to become firm. On this made land there was a very evident 
belt of maximum damage several hundred feet wide and running about northwest and 
southeast, commencing near the custom-house and ending at the Folsom Street wharf. 
One account of this belt goes so far as to trace 8 or 10 distinct lines of maximum dis- 
turbance, practically every building on these lines being more or less damaged, while 
none outside of these lines was seriously injured. 

In many places the made land settled. At the junction of Market and Front Streets, 
the ground sank for a foot or two, and there was evidence that the tide had risen in the 
adjoining lot at the same time, for a pond of water collected and remained until low tide. 
On Pine Street, near Battery, the cobbles on the south side of the street sank away from 
the curbstones to the depth of 1 foot in some places; and the asphalt sidewalk on the 
north side was twisted and torn out of all shape, and its connection with the curb-stone 
severed. (Alta California, Oct. 22, 1868.) 





1 Thos. Tennent, agent U.S. Coast Survey, in Alta California, on Oct. 22, 1868, reports it as lasting 
46 seconds and as being from southeast to northwest (nearly) in direction. 


MA. 
ee 


PORTION or SAN FRANCISCO 


THE DISTRIBUTION and DEGREE of DAMAGE, 


CAUSED BY THE 
KARTHQUAKE OF 1868 
IN RELATION TO THE MADE; LAND 








POPES 


AC 


Cy 


—F 
aiais! 





> 


= iv 
a pS 
4 7 
ta wh 
7 4 - 
Pe w.. |) 
2 
4) 


om | Ladd ys 
»>e \' - ¥ 
, ts Oa tea, 
a & 
—~S 
“ P 
c 
5 
- 
ive. 
Hig 
oa. ae 
ge 26 
in) fue 
- f; ~ - _ _) 
> lwetedale 
7 
; 7 ; - 
— or J ie 





COMPARISON WITH OTHER SEVERE EARTHQUAKES IN SAME REGION, 437 


At the corner of First and Market Streets, the ground opened in a fissure several inches 
wide. At other places the ground opened and water was forced above the surface. (San 
Francisco Bulletin, Oct. 21, 1868.) At Fremont and Mission Streets the ground opened 
in many places. (Alta California, Oct. 22, 1868.) ‘The general course of damage in 
the city was along the irregular line of the ‘‘made land,” or low alluvial soil, where it 
met the hard or rocky base beneath it. Along the line of the old shore of Yerba Buena 
Cove, we found the damage to brick buildings much the largest. (George Davidson.) 
The custom-house, at the corner of Sansome and Clay Streets, was hurled south, by 
what seemed to be an undulating motion, and plaster fell. (Bulletin, Oct. 22, 1868.) 

The outstanding portico on the east side of the custom-house was so badly shattered 
that it had to be removed; the main building stood fairly well, but one of the chimneys 
was broken across at the roof-line and turned thru an angle of over 45°. (George 
Davidson. ) 

The ground floor and the foundation of the old Merchants’ Exchange appeared to 
have taken a different motion from the upper portion. The arch over the main corridor 
appeared to have been crusht. Just underneath the center, the matting was raised 
2 inches. The corresponding arch at the south end of the corridor was also damaged, 
and there was a similar protuberance under the matting beneath it. Smaller arches 
at right angles to the main arches described were crusht in similar fashion. The north 
and south walls of the building, at the second floor, over the main arches, opened in 
large cracks. (Bulletin, Oct. 22, 1868.) 

A 3-story brick structure on the corner of Market and Battery Streets, in an 
unfinished condition, was completely thrown down. Several different reports state, 
however, that it was very poorly constructed. In the Union Foundry, on First Street 
at the corner of Market Street, most of the machinery was displaced. (San Francisco 
Bulletin, Oct. 21, 1868.) 

The floor of the Pacifie foundry was raised about 2 feet in places. The center of 
Mission Street (opposite Fremont Street) exposed an opening from 8 to 10 inches wide; 
and openings of the ground were also plainly to be seen on Fremont Street, in the same 
vicinity. (San Francisco Bulletin, Oct. 21, 1868.) 

Outside of the immediate district described above, damage to the rest of the city was 
very meager. It will be noticed in the following notes, and by a consultation of the map 
of San Francisco, plate 146, that the region of greatest agitation was confined to the 
low portions of the city, or the vicinity of some old creek bed or swamp. 

The flat between Howard Street and Mission Bay was more severely shaken than 
Russian and Telegraph Hills; but the damage, save to chimneys and plaster, was slight. 
The only serious injury on Kearney Street was done to a building on the east side of the 
street. The building was an old one. At the corner of Fifth and Market Streets a fire- 
wall was thrown down. At the corner of Fourth and Bryant Streets, walls were cracked 
and damaged; Fourth Street near Bryant opened in places and at the crossing of Harri- 
son and Fourth the railroad track settled about 8 inches, the planks between the rails 
rising about 10 inches. The Lincoln School-house (east side of Fifth Street near Market 
Street) was badly damaged, most of the chimneys being broken but none thrown down. 
The large statue of Lincoln in front of the building was ruined, but was not thrown off 
its pedestal. (San Francisco Bulletin, Oct. 21, 1868.) 

The large chimney of the sugar refinery on Highth Street fell in, crushing thru the 
ceilings. (Letter to New York Times, Oct. 21, 1868.) 

A drug store at the corner of Fifth and Folsom Streets had its entire stock de- 
stroyed by falling. The chimneys of the Mission Street public school (west side of 
Mission Street between 15th and 16th Streets) toppled off some bricks. (Alia Cali- 
fornia, Oct. 21, 1868.) 


438 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION, 


A part of the brick walls of the new Calvary Church (Geary and Powell Streets) fell. 
A small crevice opened, as in 1865, on Howard Street beyond Sixth Street. No damage 
was sustained by the dry-dock at Hunter’s Point. On the beach at the foot of Webster 
Strect, below high-water mark, a fissure opened, extending lengthwise with the water. 
The stream of a sewer running from the Laguna to the foot of Webster Street into the 
bay, hitherto clear, immediately turned inky black. (Alta California, Oct. 22, 1868.) 

The sugar refinery at North Point, a 7-story brick structure, surmounted by a tall 
brick chimney, was injured to the extent of losing 6 or 7 feet of its 100-foot chimney. 
A large fissure was made in the high bank near Fort Point and the shock was felt severely 
at the Fort. (San Francisco Times, Oct. 22, 1868.) 

At the Cliff House nothing unusual took place, with the exception of a decided com- 
motion in the ocean and an impetus given to the every-day wave which sent it well 
inland, say 15 or 20 feet above the usual mark. The shock, however, did no damage, 
not even upsetting any of the glassware in the bar. (Alta California, Oct. 22, 1868.) 

Upon Russian and Telegraph Hills the shock was not very damaging. In some houses 
on the latter ornaments were not displaced from the mantel and the inmates did not 
come to the doors. In others, books and ornaments fell down and marble mantels were 
started from their places. The oscillations on Russian Hill were more severely felt. 
There was a pretty general stopping of clocks, some cracking of plaster, and throwing 
down of light articles. (San Francisco Bulletin, Oct. 21, 1868.) 

A pail of water, two-thirds full, on the ground at the summit of Russian Hill, slopt 
over both sides. (Alta California, Oct. 22, 1868.) 

The colored Masonic Hall, Stockton Street between Pacific and Broadway, a 2-story 
brick structure, was badly wrecked. (San Francisco Times, Oct. 22, 1868.) 

From the meagerness of reports it is certain that no great loss was occasioned by the 
parting of water mains. The Bulletin for October 21 reports that the water at the 
Mission was shut off by the pipe being disconnected. In several parts of the city the 
water-pipes broke underground and caused some loss of water, but the water company 
soon had all repairs made. No fires are reported in the upper Mission district during 
the 24 hours following the earthquake. At Laguna Honda (a natural reservoir and the 
chief source of water supply, 2.5 miles west of Valencia and Market Streets) the water 
was violently agitated and the waves met in the center, throwing up a large jet several 
feet into the air. (Alta California, Oct. 22, 1868.) 

The first alarm of fire was given shortly after 8 o’clock from Box No. 26 (northeast 
corner of Clay and Battery Streets). The fire was in Wellman and Peck’s grocery (Front 
and Clay Streets) and was caused by matches. The chief damage was caused by. water. 

During the night following the earthquake, three fires occurred in the wholesale dis- 
trict, but there was no lack of water and all were quickly extinguished. 

In the Fire Commissioner’s report in the Municipal Records of San Francisco for 1868— 
1869, the following losses by fire are recorded: September, 1868, $24,229; October, 
IS68, $133,564.46; November, 1868, $19,920; December, 1868, $82,019. 

The force of the shock was distinctly felt on the bay and as far as 15 miles west of the 
heads, but no great agitation of the water is reported. The tide-gage at one of the Gov- 
ernment stations indicated no unusual rising of the tide. (San Francisco Times, Oct. 
22, 1868.) 

There was no tidal wave accompanying the earthquake. The passengers on a ferry 
steamer (off Angel Island) felt the shock and supposed for the time that they were 
aground. Many other boats reported the same experience. Two boatmen in a White- 
hall boat off Fort Point report a heavy rumbling sound coming from the water. Their 
boat was shaken and whirled rapidly around (before the rollers reached them) and 
shortly they met 3 heavy rollers coming from the northwest on a calm sea. (Alta Cali- 


COMPARISON WITH OTHER SEVERE EARTHQUAKES IN SAME REGION. 439 


fornia, Oct. 22, 1868.) The shock of the earthquake was distinctly felt at sea near San 
Francisco. Captain Tobey, of the ship Pactolus, reported being at anchor in deep water 
about 15 miles west of the Heads when the shock took place. At first it seemed as if the 
vessel were passing over a coral shoal and striking quite heavily. The noise and motion 
made it seem as if the ship were dragging, with her chains also slipping out. (San Fran- 
cisco Bulletin, Oct. 22, 1868.) The ship Cesarewitz felt the shock nearly out at the Faral- 
lones; the brig Orient, bound in, 8 miles out, experienced the shock heavily. Pilot 
Murphy, on a transport bound out, reported that the bark seemed to have struck bot- 
tom, her progress being impeded; and the ship, especially the yards and masts, trembled 
violently. (San Francisco Times, Oct. 22, 1868.) 

The total list of casualties due directly to the earthquake numbered 5, and about 25 
more occurred from secondary causes. The total loss of property was variously stated 
from $300,000 to $5,000,000. However, a careful estimate of damages made a day or two 
after the disaster, placed it at about $350,000. (San Francisco Bulletin, Oct. 23, 1868.) 


THE DISTRIBUTION OF INTENSITY THRUOUT THE STATE. 


Healdsburg. — A good shaking. Heaviest shock ever felt. (Democratic Standard, 
Oct. 24, 1868.) Lasted about 10 seconds. Vibrations north and south. Clocks stopt. 
(Alta California, Oct. 22, 1868.) 

Guerneville. — The earthquake was of great severity. It frightened my horse and 
he started to run away; but a large tree which had been cut nearly thru by choppers, 
and which they felled a few moments after the shock, was not overthrown by the shock. 
(I. E. Thayer.) 

Santa Rosa. — Severest shock yet felt. Lasted 10 seconds. Nearly all brick buildings 
in town more or less injured. Many chimneys down. (Alia California, Oct. 22, 1868.) 

Violent and somewhat protracted earthquake. Vibrations at first from west to east, 
but suddenly changed from south to north, and continued about a minute. Damage 
to property considerable. Several brick buildings cracked. At Windsor it was lighter 
than in Santa Rosa, and farther north still lighter. At Sonoma, Sebastopol, Bodega, 
and elsewhere, the shock was severe but little damage was done. (Santa Rosa Democrat, 
Oct. 26, 1868.) 

Petaluma. — Vibration north to south, 10 seconds in duration. Several brick build- 
ings injured and many chimneys. (Alta California, Oct. 22, 1868.) Oscillations from 
east-to west; 3 distinct shocks lasting in all 10 to 15 seconds. (Petaluma Argus.) 

San Rafael. — Terrible shock. Vibrations southeast to northwest, for fully a minute. 
(Alta California, Oct. 22, 1868.) 

Napa. — Violent shock in northeast direction for 30 seconds, accompanied by low 
rumbling sound. Some slight damage. (Alta California, Oct. 22, 1868.) 

Most severe shock ever felt. Lasted 40 seconds. No serious damage to buildings. 
Five miles west of Napa a number of trees were overthrown. (Napa Reporter.) 

Vallejo. — Earthquake severe. Many chimneys down. (Alla California, Oct. 22, 
1868.) Heaviest shocks ever felt in Vallejo. One chimney and some plaster down, 
Dishes thrown from shelves. Bay smooth. (Vallejo Recorder.) 

Mare Island. — Chimneys were thrown, and some buildings were considerably shaken. 
Shock accompanied by rumbling sound. 

Chico. — A perceptible moving of the earth. Lamps and dishes rattled. (Chico 
Courant, Oct. 23, 1868.) 

Colusa. — Slight shock. Not over a dozen people noticed it. (Colusa Sun.) . 

Marysville. — Shock very light; noticed by a few only. (Alta California.) 

Sacramento. — Pretty heavy shock from southeast to northwest. Plaster cracked. 


44() REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


Lasted 20 to 30 seconds. Water in the river receded, shoaling vessels, and then rose 
with a rush. (Sacramento Union.) 

Knight's Landing. — “I was running a flour-mill at Knight’s Landing in 1868. While 
the shock was not unusually severe at that place, it did some damage. The gable end 
of the mill warehouse was thrown down, not by the vibration of the quake, but by a 
pile of wheat being thrown down against it and forcing the end of the building out. I 
was out in a pasture at the time, pumping water for stock, and noting the water sloshing 
from one end of the trough to the other, I wondered as to the cause, as I had not felt 
the shock on account of the motion of my body in working the pump. On looking up 
I noticed the trees swaying back and forth, with no wind, and I knew it must be an 
earthquake. ‘There was some little loss in the town in the way of broken crockery, 
chimneys, etc. ‘The heaviest shock was along the edge of the valley near the Coast 
Ranges. In this county it was heaviest at Winters, where it demolisht John Wolf- 
skill’s house, a stone building, and did considerable other damage.” (HK. H. Eastham.) 

Woodland. —'Two severe shocks, from southeast to northwest, lasting a minute. (Alta 
California, Oct. 22, 1868.) 

Suisun. — Severe shock, north and south. Slight damage. A few brick buildings 
cracked. (Solano Sentinel, Oct. 22, 1868.) 

Solano. — Severest shock ever felt. Sudden upheaval, attended and followed for 
nearly a minute by a swaying in a north and south direction. No damage except cracks 
in walls. (Sacramento Daily Union, Oct. 24, 1868.) 

Martinez. —Some buildings damaged by cracks. Waters in front of town caused 
to dance. Fish rose to surface. (Martinez Gazette.) Court-house wrecked. (Holden.) 

Walnut Springs. — Heaviest shock ever felt. Goods in store thrown from shelves. 
(Alta California, Oct. 22, 1868.) 

Antioch. — Severe shock from southwest to northeast for 30 seconds. Several fissures 
formed in the ground. (Sacramento Daily Union, Oct. 23, 1868.) 

Benecia. — At the repairing works of the Pacific Mail Steamship Company, an iron 
shaft of one of the side-wheel steamers was lying on the ground in a north-south direc- 
tion. The earth moved from under it 9 inches, lengthwise, but in what direction is not 
recorded. (George Davidson.) 

Stockton. —““T was then 13 years old. With a younger brother and a third boy I 

had, on the morning of October 21, 1868, gone to the edge of the tule marsh about 2 
“miles southwest of Stockton, to shoot ducks. The morning flight of birds was over, 
and we were returning home. My brother had his gun at the shoulder and was aiming 
at a meadow-lark when the earth movement commenced. The lark flew up without 
apparent cause, the gun moved up and down slightly, and I at once had a feeling that 
something unusual was happening. Within a few seconds the water-fowl, hidden from 
us by the tule but in countless numbers, rose with a noise like rolling thunder and took 
flight toward the west; while 0.5 mile to the east a small band of cattle, with heads 
down and tails in the air, were racing across the country. By this time the earthquake 
was probably at its maximum, and, looking east, I could distinctly see the ground’s 
surface in wave-motion, the waves apparently moving across the line of vision. During 
the time this motion continued, it was not perceptible as a vibration to the sense of feel- 
ing. All three of us admitted, however, that the earth felt insecure under foot. We 
could detect no effect on the water surface of the swamp. Stockton escaped with only 
here and there a cracked brick wall.” (C. E. Grunsky.) 

Most severe shock ever felt. Vibration from northwest to southeast. West of Lodi 
and Woodbridge, shock was as severe as in Stockton. (Stockton Independent.) 

In a slough water was thrown into ebullition to a height of 2 feet for a few minutes. 
(Stockton Gazette.) 


COMPARISON WITH OTHER SEVERE EARTHQUAKES IN SAME REGION. 441 


Berkeley. — The State Institution for the Deaf, Dumb, and Blind lost 11 chimneys and 
2 gables, and rear walls were cracked in several places. (Oakland News, Oct. 21, 1868.) 

Oakland. — Shock preceded by a rumbling sound. Pans of milk and tubs of water 
emptied almost in a moment; trees whipt about like straws; many houses twisted 5 
or 6 inches out of square, particularly those on brick foundations. The crashing of 
falling brick at the Deaf, Dumb, and Blind Institute was heard a few blocks to the 
south before the shock was felt. Chimneys very generally down, particularly those 
on south and east sides; in some parts all chimneys thrown. Many chimneys twisted, 
if not thrown. Many brick buildings were shattered, and several wharves went down 
with loads of brick, coal, hay, etc. In Brooklyn, as in Oakland, many chimneys were 
broken off at the roofs. (Alta California, Oct. 22, 1868.) 

The drawbridge of the San Francisco and Oakland Railway was thrown out of place 
about 8 inches. (Centennial Book of Alameda County, p. 266.) 

Thruout the city chimneys and walls fell south. (Oakland News.) 

Of two-houses next each other the older one stood on posts 4 feet above the ground, 
while the other was supposed to be earthquake proof. The basement walls were solid 
and of good workmanship. The old house was badly shaken, but not injured; the 
earthquake-proof house had the basement walls cracked, all the ceilings thrown down, 
and the marble mantel in each of the rooms thrown upon the floor. (Geo. Davidson.) 

Alameda. — Shock very severe. Scarcely a house escaped uninjured. (Alta Cali- 
fornia, Oct. 23, 1868.) 

San Leandro. — The earthquake was much more severe than in Oakland or Alameda. 
Not a building escaped some injury. Chimneys fell north and south. The court-house 
was inruins. A tank 10 feet wide and 6 feet deep was entirely emptied of water. The 
bed of San Leandro Creek, which had been dry for several months, became filled with 
a stream of water 6 feet wide and a foot deep. A team of mules descending a hill 9 miles 
east of Haywards, were thrown to their knees. A rumble preceded the shock. The 
rangers on the old Peralta rancho said the crack past through the foot-hills on to Saks 
land. (Various old residents.) 

San Lorenzo.— The limbs of a sycamore tree, 24 feet high, struck the ground. 
(G. Hyde.) 

Flat irons and a kettle were jerked off the stove southward. (Mrs. Adams.) 

House and barn were both prostrated. (Mrs. E. H. Gansberger.) 

A house was thrown off its foundations. Chimneys were thrown northward. 
(E. Llewellyn.) 

Haywards. — The crack past diagonally up the Haywards Hill and crost 3 feet from 
the south corner of the old hotel; past just east of the Odd Fellows’ Building, through 
the Castro lot, tearing off a corner of the adobe house which stood where the jail now 
is, on through Walpert’s Hill toward Decoto. By the hotel the crack first opened 18 
to 20 inches, but soon closed to 5 or 6. It was of unknown depth; several balls of twine, 
tied together, with an iron sinker, failed to find bottom. There was no water in the 
fissure, for the iron came up dry. From the corner of B and First Streets another crack 
past nearly eastward toward the hills, and faded out by the sulfur spring about 1.5 
miles distant. (Mrs. Wm. Haywards.) In a general way, the crack from Haywards 
to beyond Decoto past from 100 to 300 feet above the base of the hills. Practically 
not a house was left on its foundations in Haywards. At one place south of town the 
fault showed a throw of some 3 feet. (W. H. Weilbye.) 

“Since October 5, 1862, I have lived in Haywards, Alameda County, and I well remem- 
ber the earthquake of October, 1868. Being lameand having used a cane from childhood, 
I had never walked without it until that morning. I was working in my shop at the 
time. On feeling the terrible shock, and on the impulse of the moment, I managed to 





442 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 
get out of the building and into the street, some 18 feet distant, but on recovering from 
my fright I found I had left my cane in the shop. I managed to get back into the build- 
ing, got my cane, and started for my house only a few yards away. The house had been 
thrown from its foundations, the chimney had been torn from the roof, and the porch 
had been wrencht away. Dishes were broken and everything was in confusion. I 
discovered that most of the houses were in the same condition as my own — thrown 
from their foundations, with chimneys down, porches knocked sideways, etc. All the 
while the ground was shaking and continued to shake for days and even weeks; but 
each shock was lighter than the last. On a certain piece of ground near the Haywards 
Hotel there was a common board fence, the boards abutting on the post. After the 
quake the boards lapt one over the other about 5 inches, the ground seeming to have 
been prest together that much. On going down the county road toward Oakland, we 
came to Mr. A. L. Rockwood’s house, which had been thrown from its foundation and 
one end thrown into the cellar. The house was badly wrecked. In the south part of 
the town there was a flour mill on a foundation about 4 feet high. This building was 
thrown to the ground and wrecked. On the ground which is now the plaza stood a new 
brick warehouse filled with grain from the season’s crop. The building was completely 
torn to pieces; grain was spilt from the sacks, and everything was in a mess. The 
building was 300 feet long by about 60 feet wide. A wooden warehouse about the same 
size shared the same fate as the brick. On B Street the ground opened about 2 inches, 
and water and sand were forced from the opening. Some springs were closed, while 
others were opened or made to flow more freely. Many wells were affected in the same 
manner. Mr, Charles Herman, who was in the baking business, was driving back to 
Haywards after delivering bread. Looking up the road, he saw the ground coming 
toward him in waves, and when the motion struck his horse, she went down on her knees. 
Mr. Herman thought the world had come to an end. As he neared the San Lorenzo 
Creek, he noticed that the water had been thrown out of the bed of the creek on to the 
road. 

“At San Leandro the earthquake destroyed the brick court-house, which was then 
located there. A Mr. Joslyn was killed in attempting to escape from the building. 
Many buildings were much damaged in that town as well as in Haywards. The earth- 
quake was the direct cause of the death of 2 persons in Haywards.” (George A. Goodell.) 

The crack past thru a gravel quarry practically on the summit of the first range of 
hills. (O. Hill.) 

The crack below Haywards Hotel was 12 inches wide. It ejected water and white 
sand. A fence which traversed a hill from north to south was crost by the crack, and 
had the ends of the boards loosened from the posts. Gradually these boards lapt over 
one another, until within a couple of weeks they overlapt several inches, the progress 
of the overlapping being noted from time to time by a pencil mark. The “cap” board 
of the fence was also archt up in consequence of this movement. Large waves were 
set up in the soil. The house was moved southward, while a neighbor’s was tipt north- 
ward. (D.S. Malley.) 

The rumbling preceding the shock came very distinctly from the bay, and the plain 
in that direction rolled like huge waves of the sea coming toward Haywards. (F. Allen.) 

The crack opened parallel to Castro Street, 35 to 50 feet below Haywards Hotel. The 
fence passing diagonally up the hill was shortened 6 inches. (P. McKeever.) 

A stove in the house was thrown north. (J. Wolput.) 

A crack 3 to 4 inches wide started from the Powell place and struck across toward the 
county bridge next to Nettleton’s, passing west of it; crost the creek, demolisht a fence 
completely, and past on toward the Strowbridge residence, where the house was badly 
shattered. (Mrs. Hamer.) 


COMPARISON WITH OTHER SEVERE EARTHQUAKES IN SAME REGION, 443 


The shock was from southwest to northeast. The ground opened from 6 inches to 
2 feet, and water with sand was ejected to a height of from 1 to 3 feet. North of the 
village a ridge of ground 3 feet wide was raised 2 feet. By the time the shock was over, 
nearly the whole place was in ruins. Near Hayward’s Hotel the hill shifted a good deal, 
and a crack opened for several hundred feet. On the hills there were several new springs. 
In the first 12 hours after the main shock there were 36 after-shocks. Between Hay- 
wards and Mission San Jose there were numerous cracks, so that it was difficult to drive 
a stage between the two towns. (Alta California, Oct. 22-25, 1868.) 

Mt. Eden. — All the shelving on south side of the 2 stores of the town was thrown 
down. (Alta California, Oct. 22, 1868.) 

Alvarado. — Shocks were violent. The ground opened in several places and water 
issued. (Alta California, Oct. 22. 1868.) 

Centerville. — A dwelling-house was partly destroyed and 2 stores were wrecked. 
Hotel settled 2 feet. (Alta California, Oct. 22, 1868.) 

Roberts’ Landing.—“ Our house broke in three pieces, each part falling outward. <A 
boiler of hot water was on the stove, and with the first deafening jolt, the hot water 
came my way, giving me a bath I have never forgotten. Horses fell to the ground and 
men clung to some quince trees near. 

“Captain Petersen, of the steamer San Lorenzo, who is now deceased, was walking 
along the road to Roberts’ Landing when he heard a great rumble off across the fields 
toward San Leandro. He lookt quickly in that direction, and over a mile away could 
see the great wave rapidly approaching. He rushed to the side of the road and had 
caught hold of the fence by the time the shock broke. Near him on the road a 6-mule 
team was drawing a load of grain, and all the mules fell flat and could not regain their 
feet until the great jolt was over. During the 3 or 4 succeeding days there were 150 
shocks; none, of course, with anywhere near the extent of the heavy one.”’ (R. C. Vose.) 

Decoto. — Opposite Decoto a crack appeared about one-third of the way up the slope. 
It opened 10 or 12 inches at the surface and faulted about as much on the plains side. 
The level lands waved like the ocean, and the waves seemed to approach from the south. 
(Mr. Decoto.) 

Tyson Lagoon, south of Niles. — A tank swayed north, then south, and fell. The 
lagoon parted lengthwise down the middle and threw water and mud both ways. After 
the earthquake the lagoon was dry for 3 years. It has no outlet. Rumblings preceded 
the main shock and many of the after-shocks. (Mrs. Wm. Tyson.) 

A crack went thru the old Shinn place, crost the Centerville-Niles road about 0.6 
mile southwest of the Southern Pacific Railway track, and past thru the Tyson Lagoon. 
(H. Tyson.) 

Niles. —The water from the tank slopt nearly east. Rumblings preceded the after- 
shocks. These were more severe than in April, 1906. (C. Overacher.) 

A crack past thru the Shinn and Tyson places. (C. Bonner.) { 

Irvington. — Thru the north side of town a erack split the hillside, opening 7 or 8 
inches and showing a fault of 8 or 10 inches. It crost the country road 500 feet north 
of the Southern Pacific Railway depot. Its trend was N. 45° to 50° W. From these 
low hills the crack seemed to pass over into the tule ponds north of town. The Tyson 
Lagoon dried up after the quake. The rumbling preceding the shock came from the 
north. (R. B. Crowell.) 

The railroad tracks north of the station were badly twisted for several hundred yards. 
(M. Torry.) 

In one place the crack on the hillside divided, and formed a narrow island, 8 or 10 
feet across, which dropt below the general level of the sod 8 or 10 inches. Springs were 
opened up on Mission Peak. (H. Crowell.) The crack which past thru the town con- 


444 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


tinued southward down the hillside about 0.5 mile northeast of the railway track. It 
opened 5 to 8 inches, not faulting. 

“T was then about 15 years of age. My home was near Irvington. When the shock 
came, I was alone in the house with my baby brother. My mother was in the milk house, 
about 10 steps from the kitchen door. She called to me to get the baby. Tho I was 
thrown the length of the dining-room, I managed to get the child over my arm, face 
down, and a pillow on top. Then, falling and crawling, I worked my way back to the 
open kitchen door. My mother was on the ground. Every time she tried to get up, 
she was thrown again, and the milk in the buckets was spilt over her. My two brothers, 
my step-father, and the hired man were also down and were trying to get to the house 
by crawling and falling. As I sat there, I could see the ground in waves like the ocean. 
After the main shock, I think we had 100 shocks during the first 24 hours. The ground 
opened; we traced a crack thru town, and the ground settled several inches in one 
place. Not a house was left with a chimney on it. Our safe broke thru the floor, 
and the piano was out in the room nearly to the opposite side.” (J. McD. Preston.) 

Mission San Jose. — “I was curled up in a big rocking-chair, reading, and my two 
sisters were outside playing, when suddenly there came a swaying of the house. This 
lasted only a short time; then the house began to shake in earnest. My sisters began 
to cry and scream. I jumped out of the chair to go to them, and ran from the room, 
bumping against both sides of two doors. I finally reached the porch and succeeded 
in catching hold of a post. I distinctly remember that the pump in the yard was pump- 
ing as if some one had hold of it; and small rocks on the hill in front of the house were 
rolling down into the creek. The milk pans had been resting on shelves of slats; some 
pans slipt entirely out, some only halfway. The milk and cream were on the floor. 
My brother was hauling a load of wheat to San Jose. When the earthquake was at its 
worst, he thought his team was choking down and jumped off his wagon to find he could 
hardly stand. I was told at the time that the water spurted up in the streets of San Jose, 
and out in the road between Milpitas and San Jose, to the height of several feet. The 
old Mission church, which was of adobe, was shaken down, as were several other build- 
ings at the same place. On the mountain above the old Mission, just above a place called 
Peacock Springs, a great crack in the earth appeared, which lookt as if the lower part 
of the mountain had parted and slipt down. Many times I have crost the bridge which 
was built over the crack, and stopt and thrown rocks down to see if I could tell how 
‘deep it was.” (Mrs. N. Ainsworth.) 

Along the hills back of the town and southward, passing thru the present Sinclair 
and Stanford ranches, the crack opened. Generally it was 10 or 12 inches wide, and 
faulted some 18 inches on the valley side. (A. Kell.) 

The shock was preceded by a rumble passing to the northwest. Adobe building not 
seriously injured. Crack at Irvington and on the side of Mission Peak confirmed. 
(J. Sunderer.) 

Brick store was cracked. Confirms cracks at Irvington. (8. Ehrman.) 

Chimneys fell north and south, as they did also on April 18, 1906. (S. Murphy.) 

Warm Springs. — The crack past along the foot-hills at an elevation of 350 to 450 
feet from Niles southward, back of Mission San Jose, disappearing near the county line. 
In some places the fissure showed a fault of 10 to 12 inches. (H. Curtner.) 

The warehouse and wharf on the slough fell, also Dixon’s house. Cracks in the vicinity 
of Milpitas flowed artesian water for 48 hours after the shock. (Mr. Durkee.) 

Milpitas. — Along Coyote Creek the ground was cracked from Boot’s ranch to the 
San Francisco Bay, the cracks being on the bay side and following the winding of the 


creek. As in 1906 much water was ejected from the cracks, and Coyote Creek rose. 
(W. Bellou.) 


COMPARISON WITH OTHER SEVERE EARTHQUAKES IN SAME REGION. 445 


Calaveras Valley. — Only one or two chimneys were dislocated. (J. Patton.) 

Santa Clara County. — Messrs. J. W. Hines and C. Valpey, and Miss Bennett, of San 
Jose; Mr. H. B. Valpey, of Santa Clara; Messrs. P. Anderson and C. B. Mendor and 
Mrs. W. Smith, of Berryessa, all of whom were intimately acquainted with this section 
of the country in 1868, report that there was no crack south of the county line. 

Alcatraz Island. — A rumbling sound accompanied the shock, and the island vibrated 
with a jerking motion. (Dr. L. Hubbard, U.S. A., in San Francisco Times, Oct. 22, 1868.) 

Colma. — “I was then 16 years of age and lived in San Mateo County, a mile or so 
south of the present town of Colma. With my father I was digging and sacking potatoes 
ina field. I was sewing up a sack, when my father said: ‘Look at that mountain. What 
is the matter with it?’ We felt no earthquake, but the mountain seemed to be bobbing 
up and down. A freight train was going north along the 8. P. track. Shortly after we 
had observed the mountain apparently moving, the earthquake reached the railroad 
track and the freight train appeared to gyrate like a snake. The next instant we felt 
it. The shock was very severe, throwing us to the ground and knocking over sacks of 
potatoes. A band of loose horses, including a lot of young stock, in an adjoining field, 
ran around the field at great speed, utterly panic-stricken. The house we lived in was 
in a flat some 0.5 mile from where we were at work. When we reached it, we found 
that milk pans in the pantry had been entirely emptied of their contents. Some panes 
of glass were broken and some crockery and glassware were thrown down and destroyed; 
but the house, a light frame building, was not injured. There were 48 shocks between 
the first one and midnight that night. 

“T do not now recall any serious damage done in San Mateo County. There were 
some landslides occasioned along precipitous hills and creek banks, but the buildings 
in that section were all frame, and none of them were destroyed to my knowledge.” 
(J. A. Graves.) 

San Mateo. — Vibrations from the north for 15 seconds. (Alta California.) 

Redwood City. — The court-house was wrecked and other buildings were damaged. 
The shock seemed to come from the southeast and lasted 30 seconds. (Redwood Gazette, 
Oct. 24, 1868.) 

Mountain View. — Severest earthquake yet felt. Far worse than that of 1865. Shock 
from northwest to southeast. (Alta California, Oct. 23, 1868.) 

Santa Clara. — Severe shock. Motion northeast to southwest. No serious damage. 
(Alta California, Oct. 22, 1868.) 

San Jose. — “The most terrible earth shock ever experienced in this section since 
the settlement of this country by Americans, occurred yesterday morning at 8 o’clock. 
A dense fog hung over the city at the time, when, with scarcely a premonitory tremor, 
the shock was upon us in all its force. Buildings and trees seemed to pitch about like 
ships in a storm at sea. Fire walls and chimneys were thrown down in all parts of the 
city. The heavy brick cornice of Murphy’s building at the corner of Market and Eldo- 
rado Streets fell to the ground. The Presbyterian Church has sustained an immense 
damage. The brick turrets are all down, and large portions of the steeple were pre- 
cipitated thru the roof to the floor, crushing the organ and causing great damage to the 
gallery and fixtures below. The walls of the steeple are almost a total wreck and will 
have to be taken down. $5,000 would not make good the damage done to the church. 
The large water-tank on the roof of Moody’s flour mill fell thru the roof, carrying destruc- 
tion in its course. Their wooden store-house, 100 feet in length, filled with grain, is a 
total wreck and the grain badly mixed. Two huge chimneys of the San Jose Institute 
were thrown down, one of them crushing thru into the rooms below. A portion of the 
rear wall of Welch’s livery stable fell. Otter’s unfinished block at the corner of First 
and St. John Streets, sustained a very serious damage. There is not a brick building 


446 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION, 


in the city that is not more or less injured. Brick walls are everywhere wrenched and 
cracked and many of them are ready to fall. Another such shock would precipitate 
many of our brick buildings to the ground. The brick cornice of the Masonic Hall Build- 
ing will have to be taken down, and the entire building, in its present condition, is decid- 
edly unsafe for occupancy. A large quantity of crockery and glassware was broken. 
The destruction of plate-glass windows is very great, and much havoc is done to plaster- 
ing generally. The new court-house stood the shock admirably. Some little crumbling 
of plaster decoration is all the damage it sustained. The lesson of the earth shock is: 
Erect no more high church steeples, and build no more brick buildings above 2 stories 
in height, and those only in the most substantial manner. A second but much lighter 
shock was experienced at about 10° 30" of the same day, and shortly thereafter a third 
shock of like character.” (San Jose Mercury, Oct. 22, 1868.) 

Where the Milpitas road crosses Coyote River, the banks were shaken together and 
the river-bed filled up. (San Jose Argus, Oct. 24, 1868.) 

Old Gilroy. — The building shook and rocked till the occupants became seasick. The 
oscillation seemed to be southwest and northeast, and lasted about 30 seconds. No 
damage was done beyond some broken bottles in the drug store. (Gilroy Advocate, 
Oct. 24, 1868.) 

Rumble preceding the shock came from the north. Chimneys fell north and south. 
It was fully as heavy as the shock of 1906, but not so long. The old adobe buildings were 
much damaged. (W. D. Dexter.) 

The shock was not so severe as in 1906. (Messrs. Rice, C. Wantz, Bryant, Gilman.) 

Pacheco. — livery brick house in town was ruined. (Alta California, Oct. 22, 1868.) 

San Juan. — The shock was the heaviest since 1865. Lasted 30 seconds. (Alta 
California, Oct. 22, 1868.) No chimneys fell; 2 brick walls were cracked. (C. Bigley.) 

Santa Cruz. — Severe shock from east to west, preceded by rumbling noise. Lasted 
15 seconds. Several brick buildings badly cracked. (Alla California, Oct. 22, 1868.) 
Second only to the earthquake of 1865. Vibration from northeast to southwest for 30 
to 40 seconds. 

At Watsonville chimneys and plastering suffered but little. At Kagle Glen a slide 
0 feet wide carried rocks and trees 1,000 feet. In Soquel a few chimneys were dislo- 
cated. 

_ Half Moon Bay to Pescadero.—Chimneys down or twisted, along the coast. (T. G. 
Phelps, Holden’s report.) 

Near Pescadero limbs fell from the redwoods and large pieces of rock rolled down the 
mountains. (Grass Valley Union, Oct. 29, 1868.) 

Monterey. — A smart little earthquake, traveling from north to south. No particular 
damage. (Monterey Gazette.) 

Downieville. — A slight earthquake was felt. (Mountain Messenger, Oct. 24, 1868.) 

Grass Valley.— Lamps vibrated. Vibrations from southwest to northeast. (Alla 
California, Oct. 22-24, 1868.) 

Nevada City.—Three distinct shocks felt. Also felt at You Bet. (Nevada Transcript.) 

Placerville. — Shock plainly felt. (Mountain Democrat, Oct. 24, 1868.) 

Amador County. — The earthquake was distinctly felt at Pine Grove and Voleano. 
(Alta California, Oct. 25, 1868.) 

Jackson. — Earthquake perceptible to a number of people. (Amador Dispatch, Oct. 
24, 1868.) 

Folsom. — A slight shock. Clocks stopt. (olsom Telegraph, Oct. 24, 1868.) 

Sonora. — A slight shock. (Alta California, Oct. 22, 1868.) 

Tuolumne. — Shock lasted 10 to 15 seconds. Severe. (Tuolumne City News, Oct. 
23, 1868.) 


COMPARISON WITH OTHER SEVERE EARTHQUAKES IN SAME REGION. 447 


Snelling. — Hard shock. Nodamage. (Merced Herald, Oct. 24, 1868.) 

Visalia. — Shock felt by few persons. (The Delta, Oct. 28, 1868.) 

Nevada. — At Gold Hill and Carson, shock perceptible to people awake, and a few 
people awakened. (Territorial Enterprise, Oct. 22, 1868.) 

The shock was apparently not felt in Ukiah, Yreka, San Luis Obispo, Los Angeles, 
Reno, Virginia City, Alpine County, Yuba County, Trinity County, or Oregon. 


SUMMARY. 


A review of the facts above presented regarding the earthquake of 1868 makes the 
following summary statement possible: 

1. The earthquake of 1868, like that of 1906, was due to an earth-movement on a 
rupture plane or shear zone which was manifest at the surface as a fault-trace. 

_ 2, The fault on which the movement took place was quite distinct from the San 
Andreas fault. 7 

3. It parallels the latter at a distance of about 18.5 miles to the northeast. 

4. Likethe San Andreas fault, it is coincident with an old diastrophic line upon which 
similar movements have been recurrent in time past. 

5. The old diastrophic line is marked by a degraded fault-scarp, which bounds the 
valley of San Francisco Bay and Santa Clara Valley on the northeast. 

6. Along this line there are certain geomorphic features analogous to those which 
characterize the San Andreas Rift. 

7. The fault-trace of the fault of 1868 was much shorter than that of 1906, having 
~ a known length of only 20 miles. 

8. The amount of horizontal movement, if any, was much less than on the San 
Andreas fault in 1906, and its direction is unknown. 

9. The vertical movement appears from the accounts given to have been small also, 
and to have been manifest as a downthrow on the southwest or bay side, altho this is 
not satisfactorily established. 

10. The fault-trace was characterized for the most part by a crack which in places, 
particularly on the lower ground, was superficially gaping. Associated with this main 
crack there were auxiliary branching cracks; and on the alluvial bottom-lands about 
San Francisco Bay there were numerous secondary cracks which were usually not dis- 
criminated by the observers of that day from the fault-trace. 

11. In harmony with the shortness of the fault-trace and the small movement ap- 
parent along it, the area of destructive effect was much smaller than in the case of the 
earthquake of 1906. This was true also of the entire area embraced by the isoseismal 
II R. F. While the data are insufficient for plotting the isoseismals satisfactorily, it is 
nevertheless clear that these curves plotted as ellipses on the map of California would 
have had much shorter major axes than in the case of the isoscismals for the earthquake 
of 1906; while the minor axes in a northeast-southwest direction would not differ greatly 
for the two earthquakes. We have no authentic reports of the earthquake north of 
Chico nor south of Monterey, altho perceptible tremors probably did extend further 
south. On the other hand, in a direction normal to the fault-trace the earth-wave made 
itself felt as far as the State of Nevada. 

12. The intensity was X in the vicinity of the fault-trace at Haywards. 

13. In San Francisco the chief damage caused by the earthquake was, as in 1906, on 
the made land and along the margin of the old shore and marsh border. But little 
damage was sustained by structures on the rocky slopes. 

14. The foot of Market Street, San Francisco, is about midway between the San 
Andreas Rift and the fault-scarp upon which movement occurred in 1868. The city 


448 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


has, therefore, to reckon with the latter as well as the former in its future career, and 
consequently should be doubly prudent in the location and structure of its important 
buildings. 

15. The cities on the east side of San Francisco Bay are less concerned with the San 
Andreas Rift, but are more immediately affected by the proximity of the diastrophic 
line marked by the front of the range of the Berkeley Hills. 

16. The interval between the disastrous movement of 1857 on the San Andreas Rift 
and the movement on the Haywards fault in 1868 was 11 years. 


THE EARTHQUAKE OF 186s. 


About 12" 45" p. m., on October 8, 1865, a moderately severe earthquake shook middle 
California. Most of our information regarding it is assembled in Holden’s Catalogue 
of Earthquakes. In the Sacramento Daily Union of that date it is described as the 
most violent ever experienced there. After several vibrations a second or two inter- 
vened, and the shaking was then repeated more violently than at first. The vibrations 
seemed to be east and west, but a few people thought they were from southwest to 
northeast. Clocks stopt, and there was a general feeling of dizziness and nausea. The 
same paper states that at Stockton the shock was heavy and seemed to pass from north 
to south, but that no damage was done. At Petaluma there were two severe shocks in 
quick succession, vibrating from northwest to southeast. The shock was the heaviest 
experienced up to that time. All brick buildings were more or lessinjured. The first 
shock was from the northwest to the southeast, followed by a general shaking or rolling, 
closing with a jerk. At San Jose the shock was very severe. Brick walls fell and the 
convent bell tolled. At New Almaden a large brick store-house on the hill was nearly 
demolisht. Several houses in the village were thrown down. The earth opened and 
closed again. Chimneys in different parts of the county were thrown down. (San 
Francisco Bulletin, Oct. 12, 1865.) 

At Watsonville there was a heavy shock. The earth opened in several places (second- 
ary cracks), throwing up water. At Santa Cruz the shock was apparently heavier than 
elsewhere. Every brick building was reported ruined. The motion was apparently 
east and west. The lowlands along the river opened and spouted water like geysers. 
,, Some wells went dry or were filled with sand. The tide rose very high at the time of 
the shock and fell very low immediately afterwards. (Bulletin, Oct. 9, 1865.) 

“Monterey escaped unharmed.” (Sacramento Daily Union, Oct. 9, 1865.) 

After shocks were reported at San Jose, Santa Clara, and Santa Cruz. 

There is no record of the shock having been felt at Marysville, Yreka, Eureka, or in 
Alpine County; the Mountain Messenger of October 14, 1865, states that it was not 
felt at Visalia nor in Los Angeles. The Bulletin of October 17, 1865, states that it was 
not felt in Santa Barbara. 

In San Francisco, according to the Bulletin of the date of the earthquake, there was a 
violent shock lasting about 5 seconds, followed almost instantly by another much heavier 
shock, which continued for 10 seconds or more. Vibrations appeared to be nearly east 
and west, but some experienced observers said that the movement was in the same 
direction as previous shocks — nearly northeast and southwest. The commencement 
of the shock was accompanied by a rumbling sound. During the following evening there 
were two or three slight after-shocks. The effects of the earthquake were visible in every 
street. No buildings were entirely demolisht, but the damage aggregated many thou- 
sands of dollars. The most important damage to buildings occurred at the following 
localities: 


COMPARISON WITH OTHER SEVERE 


Corner Mission and Third Streets. Upper half of 
front of 4-story brick building fell; poorly con- 
structed. 

Northeast corner Battery and Washington Streets. 
Old Merchants’ Exchange ruined. 

Beale Street, near Market. 

Kearney Street, near Sutter. 

Jackson Street and Stout Alley. 

Mission and Fremont Streets. 


EARTHQUAKES IN SAME REGION. 449 


Corner Kearney and Washington Streets. City 
Hall had front wall badly cracked and entire 
building rendered unsafe. 

Washington Strect, near Sansome. 

Market Street, near Sansome. 

Pine Street and Front Street. 

Market and Pine Streets. 

Sacramento and Battery Streets. 

Sacramento and Webb Streets. 


Battery and Union Streets. 


On the marshy lands in the vicinity of Howard and Seventh Streets the ground was 
heaved in some places and sank in others. Lamp-posts were thrown out of perpendic- 
ular, gas-pipes were broken, ete. 

It appears probable from these scant records that the seat of the earthquake of 1865 
was somewhere in the Santa Cruz Mountains, between San Jose and Santa Cruz. If 
this conclusion be accepted, it seems further probable, in the light of recent events, that 
it was due to a minor movement along the San Andreas Rift. It was probably a some- 
what less severe earthquake than that of 1868. The earth movement which gave rise 
to the shock extended neither so far south as in 1857 nor so far north as in 1906, but 
appears to have pertained to that portion of the Rift affected in 1906 rather than to 
that affected in 1857. 

The only other earthquake which can definitely be referred to a movement along the 
San Andreas Rift was that of April 24, 1890, which, according to Messrs. F. Abby and 
Charles Bigley, of San Juan, opened a fissure at that place on the line of the Rift. The 
railway bridge at Chittenden was displaced, as it was in 1906. 


THE EARTHQUAKE OF 1857. 


Information regarding the earthquake of 1857 is scant and generally unsatisfactory 
as to details. California at that date was very sparsely populated, particularly in the 
southern Coast Ranges, where the seat of the disturbance was. The only records that 
have come down to us are those of Trask, in the Proceedings of the California Academy 
of Sciences, Vol. I, 1873; a note by J.S. Hittel in his ‘‘ Resources of California,’ 1863, p. 42, 
and some notes in Holden’s Catalogue of Karthquakes. These brief notes are supple- 
mented by the statements of a few old residents who recall the event, some of whom 
were in the zone of acute disturbance at the time. The data, while insufficient for a satis- 
factory account of the earthquake, warrant the statement that it was due to a displace- 
ment or fault in the San Andreas Rift, along its extent from Cholame Valley to the San 
Bernardino Valley, a distance of about 225 miles. 

According to Dr. Fairbanks, who has recently been over the course of the Rift in the 
southern Coast Ranges, the residents along that line have either very vivid recollection 
or very strong tradition regarding the rupturing of the ground at the time of the earth- 
quake; and Dr. Fairbanks’ field observations confirm the probable truth -of their state- 
ments. It appears to have been generally recognized by people familiar with the southern 
Coast Ranges that the shock was due to or associated with the rupture of the ground, 
and the line of rupture is commonly referred to by the country people as the ‘“earth- 
quake crack.” This crack, as opened in 1857, with differential displacement of unknown 
extent and direction, is still pointed out as a remarkable phenomenon from Cholame 
Valley southeastward along the northeast side of the Carissa Plain, through the Tejon 
Pass, thence along the southwest side of the Mojave Desert, past Lake Elizabeth and 
Palmdale, to the Cajon Pass and thence to the south side of the San Bernardino Range. 
The shock was felt from Fort Yuma to Sacramento, and the total area sensibly affected 
was probably not much less than in the earthquake of 1906. It was severe both at Los 
Angeles and San Francisco. At Los Angeles shocks continued at intervals during the 

26 


450 REPORT OF THE CALIFORNIA EARTHQUAKE COMMISSION. 


day. Mr. H. D. Barrows, who was in that city on the day of the earthquake, in a letter 
dated August 5, 1906, communicates the following information as to his experiences: 


The great earthquake of January 9, 1857, in southern California, opened the ground for 
nearly 40 miles in a straight line near Elizabeth Lake. I had a brief account of it in the 
San Francisco Bulletin about February 1, 1857 — my letter (signed “ Observador’’) 
being dated January 28, 1857. 

Only one life was lost by that great convulsion of nature, a woman being killed at Fort 
Tejon by the falling of adobe walls; and, considering the colossal disturbance, very little 
damage was done to buildings here in Los Angeles. This is probably accounted for by the 
fact that our buildings were of only one story, with walls 2.5 and 3 feet thick. Atthetime of 
the great upheaval, I was in the yard at the south side of the adobe house of William Wolf- 
skill, the pioneer, near the present site of the Arcade Depot in Los Angeles. I first stumbled 
toward the west, and was almost thrown down; then, after a brief period, | commenced to 
stumble in the opposite direction. Other persons near me stumbled in similar fashion. 
The long wide corridor on the south side of the Wolfskill house was hung with grapes, and I 
noticed that they swung back and forth clear up to the rafters. Water in tanks was thrown 
out in numerous instances, clocks were stopt, etc. The movement seemed to be com- 
paratively slow, giving things time to recover after moving in one direction. If the motion 
had been short and sudden, the damage would have been appalling." 


All the houses in Santa Barbara were damaged by the shock of 11" 20” p, M., January 8. 
(Perry, Holden’s Catalogue.) 

At Visalia it was difficult to stand erect; treetops waved several feet to and fro; it 
was equally severe at places within 50 miles north and south. There were several 
shocks felt at Stockton and Benson’s Ferry, and the principal one was very severe at 
Sacramento, Los Angeles, and Monterey. (San Francisco Bulletin, Jan. 9, 1857.) 

At San Francisco the main shock was’preceded by 4 slight shocks at 11” 20" p, M., 
January 8; 11° 33", 4" 15", and 7" a. m., January 9. The main shock stopt a jeweler’s 
clock at 8" 13" 30° a.m. Prof. George Davidson, who was in the city at the time, says 
the shock was sudden and sharp, preceded by no noise. He was lying north and south, 
and felt the movement in that direction. A friend who was lying east and west was 
thrown out of bed. 

Professor Davidson also contributes the following: 


The wholesale grocery store of Goodwin Brothers faced east on Battery or Front Street, 
with its length of about 100 feet on Commercial Street. It was a l-story brick structure 
about 15 feet high, with a flat metallic roof and a fire-wall of 3 or 4 feet above and around 
the roof. There were no windows nor doors on Commercial Street. The fire wall along Com- 
mercial Street was thrown bodily from the main structure into the street. The inner edge 
of the bricks was a straight line, at a measured distance of 6 feet from the base of the wall, 
while the general mass was scattered across Commercial Street. In the hardware establish- 
ment of Philip T. Southworth, along the west side of the east wall, there was a line of nail 
kegs, every one exactly 12 inches from the baseboard. Before the shock they had been 
placed close to the baseboard. These two conditions would indicate a movement of the 
earth from the northward and westward — roughly, from the north-northwestward. I 
do not remember damages to other buildings, but am satisfied there were no serious results 
to property. Among minor details were the effects of the shock upon one of the piled 
wharves, where a lot of bar-buoys had been left. They had been rolled about in every 
direction. 


The following note on some of the effects of the shock in various parts of the state is 
extracted from Hittel’s “Resources of California,” 1863, p. 42: 


The waters of the Mokulumne River were thrown upon the bank, almost leaving the bed 
bare in one place. The current of the Kern River was turned up stream, and the waters 
ran 4 feet deep over the bank. The waterof Lake Tulare was thrown uponits shores, and the 
Los Angeles River was flung out of its bed. In Santa Clara Valley artesian wells were much 





* Los Angeles is about 40 miles from the line of the Rift. A. Cal BF 


, 


COMPARISON WITH OTHER SEVERE EARTHQUAKES IN SAME REGION. 451 


affected; some ceased to run, and others had an increased supply of water. Near San 
Fernando a large stream of water was found running from the mountains, where there had 
been none before. In San Diego and at San Fernando several houses were thrown down, and 
at San Buenaventura the roof of the Mission Church fell in. Several new springs were 
formed near Santa Barbara. In the San Gabriel Valley the earth opened in a gap several 
miles long, and in one place the river deserted its ancient bed and followed this new opening. 
In the valley of the Santa Clara River there were large cracks in the earth. A large fissure 
was made in the western part of the town of San Bernardino. At Fort Tejon the shock 
threw down nearly all buildings, snapt off large trees close to the ground, and overthrew 
others, tearing them up by the roots. It also tore the earth apart in a fissure 20 feet wide 
and 40 miles long, the sides of’which vent then came together with so much violence that 
the earth was forced up in a ridge 10 feet wide and several feet high. At Reed’s ranch, not 
far from Fort Tejon, a house was thrown down and a woman in it was killed. 


The most interesting fact connected with the earthquake of 1857 is that it was due to 
an earth movement on the same diastrophic line as that on -which faulting occurred 
on April 18, 1906. ‘The movement in 1857 was, practically speaking, along the southern 
half of the known extent of the San Andreas Rift, while that of 1906 was along the 
northern half. 


% : rep 4 4) fees rminggs ae ee 
= aa 
¢ iP “ft 
























vrai Sore eee —s 


iei meth Web care 1 e c 

x an ‘| [ae mie Ps ae a » oye 

Ds ig Raa eeeT aie hee wl di 

1a alte wk Ke bee eel ., “wate aa 

eee oAs nat eters , a 

v . wr bored 2 1 peed 

° Trek path ads | ane 

; ~ ew ee Bie emg otaciarn promi ith ae 
; + )oA0 Ae =a’ We 
E. Ta ete 

rrecpils oe Wey Womans “2 ove vine f 


a he", aye ge par 4 


piel 


My ‘3 é a ae > Gh Ve 
i d 7 1 jesb ah\ 








a 


i, 
oh job é 
™} 


i 


—_ 


> 


» 





i) 8 
=! 


. oe 
i. hg 




















ain PNA Pa Ahsan Na Pin eth Be Fy dian te 
Fe ER dt ties 






Cas 
WH UERLOY 4. a URkTa eet 
+ e AAAS ROD tate ed. i Te bala 
SRN 
+e Ge PHN toy UR Ac GS an 8 
4 wy 4 









Ay FAY nh “ 
4 eva RE 

% os RASTER 
Ne Tah AA ee maa BEY 
MM login yh 


























f 
Bas ete sea ete 
© Rabe y dew ¥ 

a 









; : ee -URBANA 
See sa ROO REE am : a 
8 





Sat an Ate Srchatt mh Waa A ae we Sony tyre a Wie cit) Sega asc 9.561.22012 Pe age 
“gee ORE EEN RUE LoD Ceara aia OSS! Cog cARTHO 










ve * Rye) 
ue Laas 
vgs ¥ aon 


Foe et 














eae Ey 
FRE Near Om 





aay 


Winns 
‘i 


y SU Rabie iye Cor bee ay 
ne Wb UR, Dey 
oe RSC ORS SARE A HE 
ANAL We Sai Oe ty 

teen SNe Ba 














Whe 
TA ed acts whee 
ee Ce Boh E Ute 
© Erne APS We 







NY SS iy 
BAS oy 
ante § ee ni \ 

puna Se yf 


a Ws i Me 



























































































tg t ; 
\ Res a 4-6 cue eS acy % es Ube 
ae Sect Ae A TO Haar ey ' be 
‘ ere re 
Pa hehet ye by ae Ret Oh \ " pile ARS te Gets ‘ 
bit oe NS HOS TRUNROs S Esso. sire 
moe atin . a Maas SPE bie sath ; Hee Ye a tr Use aed: Ota bas } ; 
hy a ; ayy oe SOUP SIR 4 ‘ ft u ‘ 
b rates et " & are i ‘ 
mes i ea My A ‘ * 
wh &; f how % ' bibl ' 
Ne ; Sine 
ae eK hd i Rene" 
4. ae We be wee Orig ‘ t 
SMT) res ren } ead ete : 
"END Co eeab Shea SRSA RAR aN ag f 
JU A ee Motte derte ont he A 
i Heo | C 
Woinieky oak 4 \ 
Sey yi rev A hi 
\ \ wee ss f 
Sigal ey Ne Woah Chee 


sh a 





i Ae ee dees Gre 
iN reel, 





© 
b cise. Weygnate 
SW 














































































































hs toeih a i 
Pet i 
ey au € 
Pens : ' 
RM bn Ti shah ohhh Ds Geis) 
Me Ape tal Ay Se re Grete PD Doge wane iene 
prinue ny M : 
ihe et ’ 
ees f 
A 0 Hee iti ‘ “ » b 
‘- * : - 
t AM A ‘ Ha letttt os, e 
Lath ae “ to i] ot. TI eyyemrurdet We "7 far 
wr eee ‘5 By RPh ef 4 + eh 4 one 
vada ts ie P my ae eek % ee nat Satiranithee Ue hee Grete ¥ 
ret G-¢ ia \ hw 
sa ebe 
ae 
‘ 4 ‘ j 
eae a 
® ' 
araNt i yt hel hy ‘ ' i 
she We i tis CAN ( ‘ 
vidi a hy My wie at : ae # | 
” HARA NG mote 
. Me Ph Brace if i? 
‘ SHIN by! e 0 mt fe Pit, esata ‘ 4 Wu 4 ¢ Me : ‘ 
Ns i ; hs) : NA 
43 ‘ ee cal : bay 
yt > ‘ ‘ 
ia : Cras an i 
oy 













7 8 
sib asset Ne at ast ny va 


5 64 Eh 
a eens eG. Bry af 


ue "ali 
















ond 
Late 
¥ 



















































































































































































































ey 
“eae 4 
heist 4 ee Kee a 
oe ae bite» 
wet i t 
a ey e 
aay uN A x i“ > 
vs ne BAG Lise einen ay ara in wis aa Pah LK ie $i Fata ‘beohe wut meta se 
ape CoN ‘Gat P4sniri G p h aif i eda " iy wh why REC apes 
inv jinn n 
4 o4 
~ 4 
a Oe 
¥ Wey Wel ay ae a he ee hoy neve ros fy 5 6 r y 
" f ig ah 
foul bt Lt . ® 
ny min i aes t 4 f, : f 
ime alge tdi a Sa) 4 % 
ty 3 ri iesteal ike cet 2: : ras 
ne itsieet ree" 1 i Sh ie ena wh oe were! 4 a, he bad 
, ’ e+ t 
; ns ‘ i ‘ t 
rede a) ah Tile | - v ve ; 
Eat bs fe ne Gidea tarts Meo Pry rit (on { SA st be 
iain Fath nian Sih pein he fet Me ‘cp hans 
ree *) " f 
i Hedi te sO Sania Le : 
‘ 5 " 
e * - cae ‘ 
vie $ 
and: ren t iat ’ Mh 
1 foeabhis 4 dey Teva wok oa ’ as 
oh ate iM a it vt 
ri ny 4 on eo 4 ‘ 
et tit? Ane ete wy! v 5 4 i 44 mr 
ee ay i ‘ ¢ 
sy bata a Oy Mee 
swan Bhs é htds vine rk : 
ALTAR eye rw f ‘ty Nee j be 
, Pah: 4 ‘ , 
See he 4 ri ee ; tat estes ab : 
io Ht bbe tat OMee A 1 
F Hq Pe eer ei ' 
ious Ey * ve ‘ Arh 9 ee f ie ary 
Dh + rat ft: ree bool i) § ' 
v mit Beant ariay re at ra ran" 4 
i arpley, ‘i ie Ds Hay Wwte wa hiya Ny ri 
‘ + tet “7 rar d y 
Wepre Clb inet %. Coad A enh ge #6 weg f . , 
ah BA sth 9 BBR ' f f 
4 fea het ‘ » . 
P en ters ~ . 
feck e tury te we ® * t : . : ’ . t ‘ A 
ee ea Grit Hebets dee YA KAR es . a thie 
AE teeth ies RCL A te eon ea pens s rf ares ‘ ‘ ; 
‘ * . > 2. 
Y ‘ 
Sei itech 
is 4 é > * 
fouey os « 
4 ven. Mined +e Ge 
(hea ees » ny ‘ ‘ . ‘ 
I La ‘ q 
el : / F * ' 
ng par ak Vike sg ORS. be ie aerils f, eae Ny ' 
AE A es ¢ SWS Mee oe ieee B28 Gv ‘ F 4 
Al Ear (CAD obah. wr es E ¢ 
ss. hive dite ob fifi " ; $ 
A bf Peery fe 1 fea Die Ghia a 1‘ e 
Cie #4 
hy , F 
t+ 
' ‘ were ° 
4 : ¥ ‘ j ‘ ' ) 
pues hh rw sar eohehee arale hich eg 
Tybee Pot Baw dice gion bn ‘ ‘ 6 eke 
ny ; 


